Data flow analysis mainly includes information flow, transmission, processing, storage and other aspects of analysis. The purpose of data flow analysis is to find and solve problems in the data flow. Most of the existing data flow analysis is achieved through hierarchical data flow graph (DFD). The specific method is to draw a complete set of data flow chart according to the business flow chart sorted out by the business flow chart and the data processing flow mastered in the corresponding investigation process.Data flow of online travel sales system: There are three data sources for system operation: ordinary users, registered users and administrators. The system administrator first saves part of the information to the database according to the needs of different users, and then publishes it. Users with different permissions can add, modify and delete these library information. All users can query information. Through the analysis of system requirements, the basic functions of the system are determined.