In order to relieve the pressure impact problem during the starting of crane slewing system, the composition of slewing system and its hydraulic system were analyzed. Based on AMESim simulation software, the simulation model of prototype rotary system was established, and the correctness of the simulation model was verified by the comparison of experiment and simulation analysis. The pressure dynamic characteristics of the motor A,B port and the brake of the prototype were analyzed. The improvement measures to improve the performance of the rotary system were proposed and verified by experiments. Simulation and experimental results show that the impact pressure of the rotary system is reduced by adopting the bypass circuit; by changing the control strategy of the system and installing one-way throttle valve in the braking circuit, the stability of the rotary system during braking is obviously enhanced, which provides reference for the improved design of the rotary system in the future.