Abstract: A forming process called closed extrusion blank forming&die forging is put forward creatively to solve problems of the knuckle forming process such as low material utilization and high energy consumption. Firstly advantages and key structure parameters of the closed extrusion were discussed in this paper. Orthogonal experimental design was applied to select the appropriate design parameters for the FEM experiments and the RBF meta-models which used Logarithmic-path function as kernel functions were obtained . The genetic algorithm was introduced into the approximate model to carry out the multi-objective optimization. The following parameters are the optimal die parameters of closed extrusion:corner radius of bar’s root R=10, length of squeeze a=112 mm, and reserved range for two sides of the punch b =83 mm, c =72 m. Feasibility of the process is proved by finite element simulation and production practice,and it indicates that this process can solve the knuckle’s filling discontent problem under the closed extrusion-die forging process.