In order to analyze the capability and to carry out fault research for two stage double nozzle flapper electrohydraulic servo valve, the overall simulation model of servo valve was established based on AMESim platform. The correctness of the simulation model was verified by the comparison of transient and steady data of output flow obtained from the servo valve capability experiment under step signal. The frequency response curves, flow characteristic, pressure characteristic and other capabilities were analyzed with simulation for frequent faults of the valve. The simulation results make the fault analysis feasible, and can supply a basis for the fault diagnosis of two stage double nozzle flapper electrohydraulic servo valve.