Abstract: In this paper, in order to meet the strict protection requirements of automotive electronic systems, the relationship between the working mode of the blocking surge protector (BSP) and the working state of the internal depletion N-type DMOS and PJFET is studied. A bidirectional BSP circuit with 600V withstand voltage, 200mA trigger current and 20V recovery voltage was built by simulation tool. The protection application of BSP on automotive CAN bus is introduced. The research results provide important reference for BSP product serialization and platform design.