The condition monitoring and fault diagnosing technique for the hydraulic system of gas pressure regulating valve was studied.The hydraulic oil temperature,hydraulic cylinder pressure,piston rod displacement,control current of servo valve and the oil pollution were selected as the parameters of the condition monitoring.The realtime monitoring of the system was realized through the realtime collection,indication recording and alarming of the monitoring parameters based on the NI cRIO realtime control system.The condition monitoring of the key parameters of the hydraulic system and the quick fault diagnosing and location were conducted by the extraction and analysis of characteristic parameters such as hydraulic cylinder pressure,displacement signal and the control current signal of servo valve.The validity and correctness of the condition monitoring and fault diagnosis is verified by the test results.