This study investigates the ballistic design optimization of three-dimensional grains of solid rocket motors (SRMs). The geometric modeling and burnback analysis of grains are performed analytically by using basic geometries like cylinder, cone, prism, sphere, ellipsoid, and torus. For the internal ballistic analysis, a quasi-steady zero-dimensional flow solver is used. Three different optimization methods are considered: real-coded genetic algorithm (GA), binary genetic algorithm and complex method. The optimization methods are applied to the problems of finding the parameters of grain geometry satisfying an objective thrust versus time profile and maximizing the parameter of total impulse satisfying the constraints of chamber pressure and propellant mass.