The problem of high voltage failure to power on BYD Qin EV pure electric new energy vehicles occurs from time to time, which has a significant impact on the normal use of the vehicle. Based on this, this article introduces the high-voltage system structure and control logic of BYD Qin EV, analyzes the types of high-voltage non power on faults, explains the diagnostic process and methods of such faults, and proposes common fault causes, manifestations, and maintenance methods based on practical cases.