According to the shift way of 3stage transmission, the scheme of its hydraulic transmission is determined. Combined with the use of threaded cartridge valve, the hydraulic transmission system was designed to integrate valve body. The valve block was designed by Solid works and was analyzed with statics by ANSYS Workbench to be conformed reliable. Meanwhile, the flow field analysis was carried out in the working flow route of the internal valve block using FLUENT, and the fluid flow characteristics during the working process were analyzed. The conclusion is received that the pressure loss for each segment of the clutch oiltaking path is almost less than 01 MPa, which proves that the design of the valve block has a superior performance.