The distributions of different axial equivalent stresses and strains were investigated by means of the numerical simulation during the forming process of SS316L seamless reducer. Then, the thicknesses of both reducers ends were analyzed under different friction coefficients. The results of simulation show that the thickness of reducers increase with the augment of friction coefficients and the uniformity of the reducers thickness is improved either when friction coefficient is small. The practical extrusion forming of reducers was performed based on the simulation results, and the production was totally complied with the relevant standard. The results indicate that the better controlling of key technology could improve the reducer formability.