Through comparing the battery management system (BMS) in existence, it concludes that every BMS has its own features, such as, interface, communication, data hand method, and so on. There is no uniform standard in the globe, so the BMS has the compatibility problems. In order to serve the problem, this paper proposed the large-scale and flexible BMS design, which can save the BMS design time and reduce the designer work strength. In this paper, the flexible hardware and software are designed, which can change the software and interface form a new BMS quickly to satisfy the market requirement. The large-scale and flexible BMS design method mentioned in this paper can accelerates the process of the BMS design, shortens the production development cycle, and satisfies the market requirement speedily.