Abstract: Based on establishment of a tool parameter database, assembled tool simulation for process equipment in precise NC machining is carried out. The tool can be assembled with the help of 3-D assembly simulation model of the part, the assembly drawing and the list of assembly tool. Practice shows that this technology can not only shorten tool preparation time in NC machining, improve the quality and productivity of a batch production for high-precision key parts, but also raise the use rate of the NC machine.