Abstract: The matrix random cracking of ceramic matrix composite was simulated by Monte Carlo model. The shear lag model was used to analyze the micro stress field of the damaged composites. The process of matrix random cracking was simulated by using computer，the effect of some model parameters on matrix cracking was analyzed，and the simulating results were compared with those of Curtin model. The results show that the final nominal crack space is between 1～2 debonded length，the final nominal crack space decreases with the increase of the minimum cracking stress，and increases with the increase of the thermal residual stress. The simulating length has little effect on the matrix crack evolution. Monte Carlo model can simulate the matrix random cracking efficiently.