Abstract: Debonding is a main form of interfacial crack growth of fiber-reinforced composites. Based on the shear-lag model and the usual loading way, the crack growth on the interface of fiber-reinforced composites under tension-tension cyclic loading is studied. According to the Paris law, the relationship between the rate of the interfacial fatigue crack growth and the number of loading cycles, the relationship between the interfacial fatigue crack growth length and the number of loading cycles, and the relationship between the interfacial coefficient of friction and the number of loading cycles are obtained. The degradation of the debonded interface and the non-uniformity of the degradation caused by fatigue loading as well as the effect of the Poisson's contraction are considered in the present analysis.