Case study method is to understand the actual situation of management by studying the cases of enterprise problems, so as to improve decision-making skills. Because in practical work, the environment faced by enterprises is constantly changing, there are many influencing factors, and the business characteristics of all walks of life are different, so the cases are very different and the types of cases are extremely diverse.

There are many ways to classify cases, and the classification methods from different angles are also different. Regarding the types of case study methods, management scholar Dr. Yu Jing (2004) concluded that different types of case study methods can be distinguished according to different classification standards. Some case study methods are only applicable to specific case study types, and some case studies can apply multiple case study methods at the same time.

(1) Differentiate the types of cases according to different research tasks.

According to the different research tasks, case studies can generally be divided into five, four or three categories.

First of all, case study methods can be divided into five types (Scapens,1990; Hersey & ampHussey, 1997): Exploratory, descriptive, illustrative, experimental and explanatory case study methods. Among them, exploring MBA case studies often goes beyond the existing theoretical system and uses new perspectives, assumptions, viewpoints and methods to analyze social and economic phenomena. This kind of research paves the way for the formation of new theories, which is characterized by the lack of systematic theoretical system support and imperfect related research results. The other four types of case studies are carried out under the existing theoretical framework. For example, descriptive case study is a case study that describes the practical activities of enterprises in detail under the existing theoretical framework; Illustrative case study is a case study that expounds the creative practice activities of enterprise organizations or the new trend of enterprise practice under the existing theoretical framework; Experimental case study is a case study that examines the implementation of new practices, new processes and new technologies in enterprises and evaluates their benefits under the existing theoretical framework; Explanatory case study is suitable for the research task of understanding and explaining the practical activities of enterprises in reality by using existing theoretical assumptions.

Secondly, according to different tasks, case study methods can be divided into four types: exploratory, descriptive, explanatory and evaluative (BaSSey, 1999). Among them, the exploratory case study focuses on putting forward assumptions, and its task is to discover new theories; Descriptive case study focuses on describing cases, and its task is to tell stories or draw pictures; Explanatory case studies focus on theoretical testing; Evaluation case study focuses on making judgments on specific cases.

Finally, some scholars divide case study methods into three types, namely, exploratory, descriptive and explanatory; Some scholars also call explanatory type "analytical type"; Other scholars refer to case studies other than exploratory and descriptive case studies as comprehensive method case studies.

Although there are three categories, four categories or even five categories of case studies according to different tasks, the connotations of exploratory and descriptive case studies are basically uncontroversial. They correspond to case studies that are beyond and completely within the existing theoretical framework, and the differences mainly focus on the classification and attributes of case study activities based on the existing theoretical framework but trying to break through and develop.

(B) according to the number of cases to distinguish the types of case studies.

According to the number of research cases, case studies can be divided into two types: single case studies and multiple case studies. Robert K. Yin (2004), an American case study expert, proposed that case study design can be divided into single case study and multiple case studies. A single case study can be used to prove or challenge a theory, or to show a unique or extreme case. The characteristic of multi-case study is that it includes two stages of analysis: intra-case analysis and cross-case analysis. Usually, a single case study is not suitable for establishing a new theoretical framework for the system. A single case study is mainly used to prove or refute a certain aspect of the existing theoretical assumptions, and can also be used to analyze an extreme, unique and rare management situation. In multi-case study, researchers should first analyze each case and its theme as an independent whole, which is called case analysis; Relying on the same research topic and on the basis of independent case analysis, researchers will summarize all cases and draw abstract and incisive research conclusions. This kind of analysis is called cross-case analysis.

In addition to the above two types of case studies, different types of case studies can be distinguished according to different procedures, steps and application methods in the process of case studies. For example, different types of case studies are distinguished according to different data collection methods. The common data collection methods are literature, file recording, interview and observation.

The different classifications of the above-mentioned case studies have formed various types of case studies. Generally speaking, researchers can use more than two analytical methods in the same case study.

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