The RVE (representative volume element) models were generated by using the equalcircle optimal circular packing scheme to characterize the microstructure of solid propellants. In order to obtain the influence laws of volume fraction and component material on effective modulus and Poisson′s ratio, a numerical analysis method for evaluating effective mechanical properties of solid propellants was developed by combining the VCFEM (Voronoi cell finite element method) and the homogenization method. The displacement result of a symmetric numerical example was compared with the traditional finite element method for validating the effectiveness of this method. The relative error between the two methods is less than 5%. The analysis efficiency is improved by using VCFEM, because it needs fewer elements. Moreover, the RVE models of different microstructures were calculated. It is found that with the increase of particle volume fraction, the enhancement effect of particles is more obvious. And the matrix material has a more significant influence than the inclusion material on the effective mechanical properties. 