The appearance of port logistics is by no means accidental. With the development of demand and modern science and technology to a certain extent, port logistics came into being. Competition and cooperation, functional integration and strategic alliance are the trends of modern logistics development, while scale is the direction of logistics development. It is in the formation of a global integrated logistics system that modern ports become more and more powerful [1].

As a transportation hub and the throat of land-water combined transport, a port is usually the intersection of various modes of transportation such as railways, highways, waterways and pipelines, and its capacity is restricted by the capacity of various modes of transportation linked with other modes. On the other hand, port capacity also affects the capacity of various modes of transportation connected with it. It can be seen that the port plays an important role in the whole comprehensive transportation system and its role in promoting regional economic development.

With the global transportation service entering the era of integrated logistics, the role and position of ports in social and economic development have undergone profound changes. As the main link in the global integrated transportation network, the function of the port has changed from the traditional transshipment place for loading and unloading goods to the role of integrated logistics center, and it is an inevitable trend for the port to carry out logistics services in the future [2].

The typical modes of port logistics in China are mainly divided into the following categories:

1. 1. 1 International Shipping Center

Contemporary international shipping center refers to a port city with hardware facilities such as container hub port with dense routes, deep-water waterway and collection and distribution network, and software functions such as finance, foreign trade, service and information of delicious shipping services. International shipping center is a developing concept. With the changes of the times, the international shipping center is gradually evolving from the first generation to the second and third generation. Judging from the development of China's international shipping center, the main functions of the first generation international shipping center are shipping transit, cargo distribution and warehousing. The main function of the second generation international shipping center is processing and value-added. The third generation international shipping center not only has the functions of the previous two generations, but also has the function of comprehensive resource allocation.

International shipping centers are always closely related to international economic, trade and logistics centers. Typical shipping centers in the world are built on international metropolises facing the ocean and with developed shipping industry. At present, among the major international shipping centers in the world, there are three basic modes:

The first focuses on market transactions and the provision of shipping services. This model is special, formed by long history and human conditions, and is unique among the international shipping centers in the world, namely London International Shipping Center.

The second is the hinterland cargo distribution service, that is, the hinterland international shipping center, such as Rotterdam International Shipping Center and new york International Shipping Center.

The third type is mainly transit, that is, an international shipping center in transition, such as Singapore International Shipping Center.

From the comparison of three international shipping centers, it can be seen that the choice of basic mode of international shipping center is stable with historical changes. For example, Rotterdam and new york are always based on the hinterland, while Singapore is always based on medium-sized transformation. This fact shows that in the choice of international shipping center mode, the regional conditions of ports were and still are one of the important decisive factors.

1. 1.2 virtual supply chain alliance

The main target of virtual supply chain is small and medium-sized enterprises. Most small and medium-sized enterprises can't become the core enterprises in the whole supply chain due to the limitation of their own scale, and their cooperation exists in virtual form.

With the development of economic globalization, shipping enterprises have formed strategic alliances in various ways. At the same time of industrial expansion, it also promotes the competition and continuous integration between supply chains, and finally promotes the port logistics industry to enter the stage of industrial development. However, port logistics service is not a single system, it is a systematic project with a complete supply chain. It is difficult to realize all the functions of port logistics only by a single system, which requires enterprises to cooperate and form a strategic alliance. With the growing strength of enterprises, the distribution network of world logistics has been improved by constantly exploring the market. At this time, enterprise alliances and mergers and acquisitions have become the means of enterprise competition, and port logistics has also developed in the constant competition.

Large-scale ports are ahead of the construction of Lingang logistics park. Combined with their superior natural conditions and hinterland economy, they have enough ability to develop services to customers, so they are regarded as the core enterprises in the supply chain. Although the central port is also stepping up the development of logistics, due to its own conditions, it does not have the corresponding operational capacity. According to the theory of supply chain management, small and medium-sized ports, based on information technology, form a virtual supply chain alliance through cross-regional and functional complementary combination with other nodes in the logistics system. It can also provide comprehensive logistics services in the modern sense.

1. 1.3 port logistics network layout mode

Port logistics network model is a cross-regional port logistics network layout. Mainly for those port owners who have scientific port management concepts and abundant funds, through the establishment of cross-regional port logistics networks around the world, the high profits of port logistics can be obtained by using cluster advantages and scale benefits. Joint ventures can also rely on strong economic strength to complete the structure through strong alliance.

According to the analysis of the existing situation, different investors are the main basis to distinguish the layout mode of port logistics network. The first logistics network layout mode is investors with shipping company background, such as Maersk, which is the largest container shipping company in the world. Maersk started with shipping, and gradually penetrated into port management by using its global shipping network. At present, Maersk has container terminals in important ports around the world. The second mode of logistics network layout is investors with the background of port operators, such as Hutchison Whampoa Port and China Merchants International. Hutchison Whampoa Port started as a container terminal in Kwai Chung, Hong Kong, and then introduced its successful experience management to the world. At present, its port operation has formed a very large global port network, which plays an important role in maritime traffic. Its business covers more than 20 countries in Asia, the Middle East, Europe, America and Africa, with 42 ports and 247 berths.

1. 1.4 district-port linkage logistics mode-tax declaration port area

The so-called port linkage means that some areas adjacent to the special planning department of the bonded port area are used to develop warehousing and logistics, most goods entering and leaving the port area are exempt from customs duties, and value-added services such as packaging and processing can be provided in the free port area. Give full play to the advantages of regional location and bonded area policy, improve the efficiency of port logistics and promote the coordinated development of port and shipping industry. With the development of economy, bonded logistics park will be fully integrated with free trade zone.

Bonded area is a special customs supervision area approved by the State Council, which is set up in a port area open to the outside world and a specific area connected with it, and has the functions of port, logistics and processing.

Bonded area has the functions of logistics, foreign trade, international procurement, distribution, international transit, monitoring and after-sales service and maintenance, commodity display, research and development, processing, manufacturing and port operation.

1. 1.5 logistics center mode

At present, there is no standard definition of logistics center in China, and places with large scale and multiple logistics service functions can be called logistics centers. The function of logistics center is to gather and distribute goods on a large scale. Based on this view, the logistics center should meet the following requirements: mainly serving the society; Perfect logistics function; Perfect information network; Large radiation range; Few varieties, large quantity; Strong storage and throughput capabilities; Unified management of logistics business.

However, not all ports are suitable for developing logistics center mode, which requires certain conditions. Only a few ports with superior geographical location, suitable water depth, good collection and distribution conditions and a certain degree of economic development in the hinterland are suitable for adopting the logistics center model [3].

Therefore, at present, all the major ports in the world, including China, have accelerated the development of port logistics, and regard the rapid and sustainable development of port logistics as the top priority of port future development and the most effective way to maintain port competitiveness [4]. However, the port logistics service is not blindly imitating and comparing, but should seek the port logistics development strategy suitable for the port's own situation according to local conditions, which is especially worth pondering and studying for small and medium-sized ports. With the frequent exchange of foreign trade, port transportation has developed rapidly, thus giving birth to port logistics industry. China has a coastline of 18000 km and an inland waterway of10000 km, which undertakes 9% of domestic trade transportation and more than 85% of foreign trade goods transportation, and there are more than 460 commercial ports along the coast. The development of ports and logistics are complementary and mutually reinforcing. Logistics involves comprehensive transportation, and the logistics of foreign trade goods takes the port as the best intersection. Many coastal ports and large inland ports are the freight centers and transportation hubs of public rail and water transport. It can be said that the port is a very important link in the logistics chain, and the development of logistics can not be separated from the service of the port. The rise and development of logistics has created new opportunities and put forward new requirements for the further development of the port.