In order to improve the consistency of the commissioning performance of the engineering application products of the deflector jet servo valve, this paper studies the influence of the deflector of the front stage of the deflector jet servo valve on the performance of the front stage and the whole valve at different positions of the jet disc. By using CFD simulation software, the Flow field characteristics, pressure gain and flow gain of deflector jet amplifier under different deflector positions deviation are analyzed. MATLAB/Simulink is used to model and simulate the deflector jet servo valve, and to further analyze the influence of differential pressure and flow characteristics of the deflector jet amplifier on the flow characteristic curve and dynamic performance of the whole valve. The simulation results show that when the deflector is close to the receiving port of the jet disc, the pressure gain and flow gain of the deflector jet amplifier are reduced, and the dynamics of the servo valve is also reduced. According to the simulation analysis results, suggestion is proposed to standardize the position requirements of the deflector in the jet disc in the commissioning, so as to improve the performance consistency of the servo valve.