The structure of a certain type of servo valve end cover was introduced.The structure stress condition at the position was analyzed.The effect of preloading torque on the stress and strain of the end cover structure was simulated using finite element software.Through analysis,it is concluded that a large preload torque not only causes the damage risk to the end cover material,but also causes the change of the mechanical zero position of the servo valve,thus adversely affecting the stability of the servo valve performance.By analyzing improvement measures,appropriate preload torque and anti-loosening measures were selected.The practical results verify the effectiveness of the improvement measures.