In order to study the degradation law of residual bearing capacity of steel-concrete composite beams under fatigue loading, the classical steel beam and concrete slab bearing capacity degradation model and the fracture mechanics-based bearing capacity degradation model considering the initial defect of studs were taken to study. By considering the residual ultimate bearing capacity calculation model after degrading into incompletely sheared structures under fatigue loading, a prediction calculation method for the residual bearing capacity of composite beams was established. The validity of the proposed prediction method was verified by comparing the fatigue test data of five typical test beams. On this basis，some parameter analyses of the key influencing factors were carried out. The results show that the calculation method of bearing capacity proposed in this paper has high accuracy and the error is within 8%. Under fatigue loading, the strength of each component of composite beam is degraded at different rates. The stud degrades the fastest, the steel beam is the second, and the concrete slab is the slowest. The degradation degree of the bearing capacity of the composite beam in the early stage of loading stage is dominated by the steel beam, and it is dominated by the studs in the later stage. The degradation rate of the bearing capacity increases with the increase of the loading times. The growth of the bearing capacity in the early stage is slow, basically in a linear distribution, and later it increases rapidly in an exponential manner. The ratio of later bearing capacity attenuation to total attenuation can be more than 70%. The stud spacing（degree of shear connection），initial stud defects, and load amplitude are important factors in controlling the degradation of fatigue capacity. They are necessary to be controlled in engineering design to satisfy the normal operation of the bridges.