A mesomechanical modeling approach was applied to estimate the influences of interfacial chemical reaction and interfacial bonding strength on tensile behavior and strength of fiber-reinforced metal matrix composites. First, a fracture mechanical model of single fiber coated with thin brittle surface layer was applied to describe strength of fiber on which interfacial reaction layer or artificial coating layer exists. With this model, influences of interfacial bonding strength between fiber and surface layer, difference in mechanical properties between fiber and surface layer, thickness of surface layer and discontinuity of surface layer on fiber strength were clarified. Second, a fracture model of multi-fiber composites in which shear-lag-analysis, fracture mechanics and a Monte Carlo simulation method were incorporated was applied to describe the fracture process and strength of composites. With this method, the influences of interfacial bonding strength between fiber and matrix in association with scatter of fiber strength, interfacial chemical reaction, ductility of matrix and volume fraction of fiber on fracture mode and strength of composites could be expressed successfully.