Abstract: In the single fiber composite fragmentation test （SFCFT）, the fiber fragmented randomly with the load increasing and the number of fiber fragments saturated under some load （The number of fiber fragments didn’t increase）. This test was commonly used to characterize the interfacial property between fiber and matrix. For this test, the stress transfer analysis was done with the elastic-plastic shear-lag theory under the consideration of the real performance of component materials (elastic-plastic of the matrix). So the more true form of stress distribution in the fiber axial direction and at the interface between fiber/matrix could be obtained. The heterogeneity of fiber strength distribution was considered also and the random fragmentation process in the test was simulated with the method of Monte Carlo based on the analysis of stress transfer. The relationship between load and the number of fiber fragments is forecasted. The anastomosis of result between simulation and test is achieved. So it is manifested that the stress analysis and simulation method are valid.