Machine tool is the basic equipment of machinery industry, playing very important role in today's manufacturing, and its variety, quality and processing efficiency directly affects economic benefits and the technology level of the mechanical industry production. The modular machine tool is widely used in the industry, and its production efficiency is increased by several times or even several times than the common machine tool, with such processing methods of multi-axis, multi-knife and multi-process. This paper designs the small combined machine with a set of turning, milling, drilling and grinding by PTC's 3D software, namely Pro/Engineer. At last, the technique of the interference analysis and visual simulation has been carried on, verifying the feasibility of the machine design. The machine tool is mainly used to meet the needs of processing the small parts in scientific research, teaching unit or small repair industry, not only improving the machining efficiency, but also saving space and processing costs.