In order to carry out the factory test for the rotary joint of construction machinery,a special test system was designed and simulated to test the change of internal leakage pressure and flow under load.This system was designed for bearing 42 MPa high pressure engineering machinery rotary joint,it had low pressure and high pressure test hydraulic circuit;a hydraulic station was designed and temperature rise check was conducted;in order to shorten the design cycle,Pro/E software was used to design the 3D integrated block of the high and low voltage system,and multi-angle detection was conducted to detect whether the internal channel interfered.At the same time,the AMESim software was used for the simulation of the hydraulic test system,and the simulation model of the hydraulic test system was established.Finally,the relationship curve of the leakage flow and pressure change in the rotary joint was obtained.Simulation results show that the designed test system meets the factory test requirements.