The hydraulic valve controls the pressure, flow and direction of the fluid in the hydraulic system, so the performance of the hydraulic valve plays a vital role in the performance of the whole system. The steady flow field analysis model of different valve opening in the inner flow channel of a hydraulic valve was established by using a type of slide valve type multiplex valve. Based on the FLUENT software, the distribution law of the pressure and velocity in the whole basin of the valve under the opening of different valve ports under the large flow condition was analyzed. The numerical simulation of complex flow field in throttle port 1 is carried out.