Abstract: With the development of new technologies in CNC machine tools and the widespread application of industrial automation, the level of automation of CNC machine tools has been significantly improved. An increasing number of CNC machine tool protective doors are required to adapt to various automated scenarios to meet the demands of unmanned production. This paper describes the current development status and structural characteristics of automatic protective doors, compares three main types of automatic door structures, and optimizes the pneumatic door structure of a vertical machining center based on economic considerations. The optimized pneumatic door features stable and reliable structure, accurate signal acquisition, easy installation and commissioning, convenient maintenance and operation, and low cost. It can improve machining efficiency and provides an efficient and feasible solution for the design of automatic door systems for vertical machining centers, contributing to the enhancement of machine tool automation and intelligence levels.