The die model characterized with high design efficiency and strong correlation plays an important role in simulation and machining. Because of the complexity of structure and the changing shape of flow channel, current design tools lack in the level of automation so that design of an extrusion die is a nontrivial task. In this paper, an integral design method is proposed to improve the design efficiency and model correlation. The computer-aided design (CAD) system for plastic profile extrusion die is designed and implemented by integrating Visual Studio 2010 (VS2010) and Unigraphics NX (UG). The closed loop recognition algorithm (CLR), multi closed loops intelligent recognition (MCLR) algorithm, and multi closed loops matching (MCLM) algorithm based on feature recognition are proposed to realize automatic generation of ruled surface in flow channel. The integral design and automatic generation methods of die set are proposed to facilitate efficient formation of different structures and process holes. The particle swarm optimization (PSO) algorithm is put forward to obtain best position and specification for the interference parts. Three modules (integral sketches, integral flow channel, and integral die set) are developed, which focus on integrating the proposed automation design methods into their framework. A case application on die design is used to illustrate the proposed method. The results show that the developed CAD system not only improves the design efficiency of extrusion die but also enhances the design quality.