As an important part of CNC machine tools and machining center, automatic tool changer is the basis to realize continuous processing of multiple machining operations. The design system development of tool magazine is an engineering of complex system. Based on the secondary development technology of UG, this paper developed the design and management system of tool magazine and realized the standardization and the process of design procedure. After introducing the basic idea of design system development, this paper presented function modules and design workflow of tool magazine respectively. The management system for tool magazine was given next. UG-based development of tool magazine for CNC machine tools can meet the design need and improve the design quality effectively.