Abstract: The solenoid valve controls the cut-off and circulation of gas as the core component of gas storage and sup-ply unit of the active potential control system.The operating state of the solenoid valve affects the effectiveness and reli-ability of the entire system directly.Therefore,on orbit real time diagnosis of solenoid is indispensable.This article pro-poses a technology of on orbit real time diagnosis of solenoid based on wavelet analysis,which determines the fault sensi-tive frequency band of solenoid valve through wavelet and power spectrum analysis.A filter is designed to extract effec-tive information.The purpose of on orbit real-time diagnosis of solenoid valve s is achieved through the processing and analysis of effective information.At last,this method can realize the diagnosis of different types of solenoid valves quick-ly and effectively,and improve the reliability and maintainability of the system.