Abstract: With the development of new technologies in CNC machine tools and the wide application of industrial automation, the automation level of CNC machine tools has been significantly improved. More and more protective doors of CNC machine tools need to be adapted to various automated scenarios to meet the requirements of unmanned production. This paper expounds the development status and structural characteristics of protective automatic doors, compares three main types of automatic door structures, and optimizes the pneumatic door structure of vertical machining centers based on economy. The optimized pneumatic door has the advantages of stable and reliable structure, accurate signal collection, simple installation and debugging, convenient maintenance and use, and low cost. It can improve the processing efficiency of machine tools and provide an efficient and feasible solution for the automatic door device of vertical machining centers, which is conducive to the improvement of the automation and intelligence level of machine tools.