A modeling methodology of polycrystalline aggregate has been studied to define the representative volume element (RVE) within finite element analyses of a periodic microstructure which enable us to estimate the deformation state of the microstructure and the corresponding macroscopic material response. In general, a polycrystalline aggregate contains multiple crystal grains and its heterogeneity is defined by the difference of crystallographic orientations. In this study, a modeling approach has been developed to generate a morphology of a periodic polycrystalline aggregate on the basis of the given frequency distribution of grain size with Voronoi tesselation and also finite element mesh under the constraint of periodic boundary condition.