The cold closed-die forging process of the gear is a kind of new technique of the precise forming of gear in recent years. In this paper, the cold closed-die forging process of differential satellite gear in car was analyzed through numerical simulation method. Forming mold was designed with Pro/E Wildfire2.0 which included four components : upper punch, lower punch, tooth shape upper die and lower die for Normal Cone. The three-dimensional models of satellite bevel gear mould were built and imported into numerical simulation software DEFORM-3D. Because the gear has the uniform circumferential features, in order to save time and improve the accuracy, only one tooth was simulated, and the full simulation outcome of 10 teeth was mirrored from this one. Through the numerical simulation analysis of DEFORM-3D, the instantaneous deformation and stress filed were gained. Forming defects were forecasted and the cold closed-die forging rule for satellite gear used in car was obtained which can provide effective references for no-flash cold forging process of planet bevel gear and the mold design.