In this research, we report on the development of simulation system for performance verification of BMS(Battery Management System) which is utilized in electric vehicles. In the industrial circles, a manufacturer of BMS typically tests their system with real battery packs. However, it takes a long time to test all functions of BMS. Here, we develop BMU(Battery Managament Unit) as an embedded board, which will be installed in electric vehicle for controlling battery packs. All other environment factors for testing BMU are developed in softwares in order to reduce the term of test. Especially, the proposed system consists of cell simulator and CMU(Cell Management Unit) simulator which simulate real battery cells and control battery cells. These simulators enable the BMU to test more battery cells. In addition, proposed system provides diagnosis program in order to diagnose and monitor the condition of BMS which makes the test of BMS more easily. In order to verify the performance of the developed simulator, we have performed the experiment with real battery packs and our simulator. Through comparing two results of experiments, we verify that developed simulator shows better performance in terms of less amount of testing duration though having high reliability.