The contact of the main circuit breaker of EMUs will produce a great impact force in the closing process, which will cause bounce of the moving contact and lead to arc pulling between the contact, resulting in a large number of hot burns of contact, which will cause fault of the circuit breaker and cause EMUs to stop during operation. To solve this problem, virtual prototype technology could be used to effectively predict and evaluate product performance in the design stage, so that the design scheme could be optimized. Based on the research and analysis of a certain type of main circuit breaker in the development project of high voltage electric box of EMUs, the virtual prototype mathematical model of main circuit breaker was established by using the combined simulation technology of Adams and AMESim, and the possible bouncing problem of circuit breaker was analyzed and optimized in advance, so as to reduce design defects and costs, shorten test cycle and improve product reliability.