Based on the analyzed transmission process of spindle head and combined with the analyzed assembly process of spindle box, it determined the relationships of transmission and assembly between the various components of the spindle head. Firstly, using software of computer-aided design (UG6), it established a 3D parts library of spindle box of machine tool. Secondly, we had been developed dynamic simulation and power transmission simulation software of the assembly process of the spindle box of machine tool. It could realistically reproduce the disassembly process and the power transmission process of spindle box of machine tool when running the software. The software not only could be used for the old products to analysis and improvement, but also could be used for development of new products, and to some extent, the prototype could be replaced by it. The software was one of the essential tools for both the training of related employees and teaching of mechanical engineering students.