Abstract: Due to its special structure，the electro-hydraulic servo system of gun pitch has serious velocity nonlinearity，which not only leads to different equal amplitude rotation time in different angle intervals，but also seriously affects the dynamic tracking performance of the system. Based on the analysis of the principle of pitching electro-hydraulic servo system，the mathematical model of pitching servo system motion is established，the nonlinear motion law of pitching electro-hydraulic servo system is obtained，and the suppression method of velocity nonlinearity of pitching electro-hydraulic servo system is proposed. By introducing nonlinear observation and nonlinear compensation links，the velocity nonlinearity of pitching electro-hydraulic system is well suppressed，The control characteristics of the system are improved. The simulation and prototype experimental results show that this method has good control effect，can suppress the nonlinearity from the speed master output by the position loop to the rotation speed master of the pitching body， and realize the linearization from the speed master output by the position loop to the rotation speed master of the pitching body，so as to significantly improve the rotation and dynamic tracking performance of the artillery pitching electro-hydraulic servo system.

Key words: gun, pitching, electro-hydraulicservosystem, nonlinearsuppression