Structural integrity is one criterion of vital importance for solid motor. It is shown that the optimization of grain shapes and material properties can greatly improve the structural integrity. Owing to particularity of shape optimization, the Basis Vector which guides the optimization procedure is introduced. The auxiliary model which is used to help generate basis vectors is also designed. Based on the characteristics of solid motor and its loads conditions, the plain-strain model of the star is built. Several sensitivity factors of the shape parameters are studied, and the optimal schemes are discussed later. The results obtained will offer guidance to the structural integrity analysis and optimization design for solid motor. The methods and conclusions are beneficial to the designers and manufacturing of solid motor.