Finite Element Modeling(FEM)model of TATB based polymer bonded explosive(PBX) with microstructure similar to the true one were obtained by a representative volume element (RVE) method. Two-dimension RVE, considering the fraction and distribution of the fillers and pores was established. Effects of pore structure parameters (pore size, pore space distribution and porosity) on the effective elastic modulus of TATB based PBX were analyzed. Result shows that pores in binders lead the TATB based PBX to deform easily. With the increase of porosity, the effective elastic modulus decreases with exponential distribution. And at the same porosity, pore space distribution has great effect on the effective elastic modulus of TATB based PBX, which can drop by more than 50 percent when the pores distribute in the interface between binder and explosive crystals. The impact of pore size is small to the effective elastic modulus of TATB based PBX.