In the process of SRM (Solid Rocket Motor) grain configuration design, high loading fraction always gives rise to high stress and train in the grain, and the structure integrity of grain turns hard to satisfy. To solve this problem, the integration of GA (Genetic Algorithm) and parameterized modeling method was applied to shape the optimization of the wheel shape grain. Parameterized finite element analysis model was constructed by PCL (Patran Command Language), the secondary development tool of MSC.Patran. Based on the model, the finite element mesh could be established and the maximum strain and loading fraction of grain could be exported when the geometric parameters were given.This made it convenient for GA to call, as a function. A shape optimization of a high loading fraction wheel shape grain was carried out, and the optimal grain was found. The maximum strain of the optimal grain, under low temperature load,was 30% less than the initial grain's. Meanwhile, the loading fraction remained the same. The results show that the method presented is feasible and available,and it can be applied to SRM grain configuration design of all sorts.