A pole assignment method based on ITAE model polynomial was proposed according to the large range of load parameters of a rocket launcher electro-hydraulic servo system. A digital controller was designed to overcome the disturbance effect caused by the unbalance torque and inertia, and the electro-hydraulic servo gun was quickly positioned. Combined with the system precision requirement, the parameter selection method was proposed, and the optimal range of sampling frequency of the system was 11 ~ 17 times the input signal bandwidth. The characteristic polynomial frequency band was at least 0. 3 times the sampling frequency. The test results showed that when the adjustable gun without overshoot, the precision could be controlled within 0.2 mil, and the adjustment time was less than 0.5 seconds, which could satisfy the design requirement of aiming digital controller.