Abstract: According to the theory of quadratic programming of finite element method，employing the multi-branch substructure technique，considering the frictional forces，establishes and calculates entire 3-D contact FEM model of driving gears of Shaoshan 7 electric locomotives，the different contact status of tooth’s surface influenced by different supporting is analyzed．The main results indicate that the supporting has evident effect on the contact status such as slide，contact stress, contact zone，load distribution and so on．Meanwhile，it is manifested that substructure technique is suitable for gear system which is composed of many homology parts and has advantages of calculating large-scale structure and high efficiency．

Key words: Contact analysis Entire 3-D model, Finite element method, Gear system, Substructure