Abstract: The structure characteristics of one shaft part with several oversized section change steps apply to starting motor of new energy vehicles, and its technological difficulties of cold extrusion technology are analyzed, also the design main points of its cold extrusion technology on technological process, forming blank and cold extruding die are elaborated. The compound cold extrusion dies of preforming, upsetting and cold extruding are designed. The compound cold extrusion process are simulated and analyzed by using the Three-dimensional plastic finite element and the numerical simulation analysis software. The structures, sizes and parameters of forming dies are optimized and improved, the forming problems are solved by this. The purposes of reducing the cost of production and processing greatly, and energy conservation and environmental protection are attained，and a strong foundation is laid for the mass industrialization in future.

Key words: Compound cold extrusion technology, Industrialization, Oversized section changes, Shaft part with several steps, Three-dimensional finite element and numerical simulation