In order to complete the offline rapid detection and maintenance task of a certain type of special vehicle power-on control system, a set of detection and diagnosis system is developed. Simulate the generation of input discrete signals, send the fault code of each subsystem, collect the output voltage and output discrete signals to complete the function detection of the power-on control system. Reproduce the power-on and power-off time sequence control, switch control, state feedback, state display and other functions of the power-on control system in an offline state, automatically determine the test results and give maintenance instructions. The actual maintenance application results show that the system has the characteristics of simple operation, high degree of intelligence, fast and efficient detection and diagnosis, and can complete the required test items, and the test results meet the technical requirements.