Recently the application of lever cam ass’y made of the high-functional polymer is increasing internationally to improve the productivity and weight reduction. But the application of injection molding of lever cam ass’y in our country is not reported yet because of the lack of the optimal selection technique of proper material and the optimal design of injection parameter. In order to solve the problem, the injection molding simulation is used. The modification of gate position and rib thickness was done and the parameters like injection time, injection temperature, packing pressure and cooling time were changed. As a result, the comparison between models was done and the optimal shape of lever cam ass’y was developed.