For the characteristics of small size, more forming steps and mass production of small casing part, the forming process of multistage cold upsetting and extruding for small casing part was proposed, and two schemes of sixstage cold upsetting and extruding process were designed based on the plastic forming theory. Then, the forming process of casing was simulated by the finite element software DEFORM2D, and the metal flow laws, the forming load and the distribution of forging streamline distribution of two process schemes were analyzed. The simulation result shows that the casing is filled with fullness and without folding, and the distribution of forming load is reasonable by the ‘twice backward extrusion+ final upsetting’. The verification results of the process experiment indicate that the simulation results are consistent with the experimental results, and the accuracy of the numerical simulation is verified to provide guidance for the actual production.