Abstract: As the key part of automatic transmission hydraulic control system, the valve body has complex structure and shape, many internal holes and high dimensional accuracy requirements due to its working function. Most valve holes are multistage steps, with many through holes and thin hole walls, so deformation and burr are easy to appear in the processing process. Taking PCD reamer machining the valve core assembly hole of valve body as an example, the cutting simulation software is used to simulate the cutting process, and the influence of cutting parameters and geometric structure parameters on cutting force and cutting temperature is analyzed, so as to optimize the tool structure parameters and cutting parameters. The structure and cutting parameters of the original cutting tool are improved, and the process scheme and tool to ensure the machining quality of valve core assembly hole are finally obtained.