The teaching methods of online education mainly include: (1) non-real-time (asynchronous) teaching through the Internet, and using resources such as web pages and courseware provided by online teaching platforms. (2) Two-way or one-way real-time teaching through satellite, Internet and video conference system. (3) Real-time or non-real-time teaching through mobile communication tools such as mobile phones. (4) Answer questions through centralized face-to-face tutoring. The vast majority of pilot universities generally adopt two or more teaching methods in the implementation of online teaching, forming a mixed teaching mode combining online and offline, fixed and mobile, asynchronous and synchronous, decentralized and centralized.