To decrease the performance loss such as specific impulse caused by oxidizer fuel ratio deviation from optimal value during the working process

a hybrid optimization algorithm based on clonal selection algorithm(CSA) and differential evolution(DE) was proposed in this paper

which was called differential clonal selection algorithm(DCS).An optimization model and a scheme for grain design were established

and penalty function was adopted to eliminate the restrictions. The algorithm

model and frame were applied to a hybrid rocket grain design

and the result indicates a good performance of the algorithm and scheme. After the optimization

excrescent propellant ratio and combustor pressure are reduced

the working condition of combustor and nozzle is meliorated

and an average specific impulse increase by 1.2 percent.