In order to solve the problem of instability and low controllability of the output speed fluctuation of the oil motor in the work of the hydraulic system of the warship ammunition for the large caliber ammunition,on the basis of the understanding of the working principle of the ammunition box hoister,by replacing the quantitative pump as the variable pump and adding the speed sensor and PID controller,the hydraulic system structure was improved.The mathematical model of the system was established by using the transfer function.The system simulation model was established based on Simulink.The motor output parameters were simulated.The results show that the improved system output is more stable and sensitive,and it has a certain feasibility.