Abstract: Fiber reinforced polymer composites are widely used in the fields of aeronautics, astronautics and marine technology engineering. Long-term cyclic load in hygrothermal environment is a critical problem for composite structural design and analysis, which has a significant impact on the strength and stiffness of composite structures. In the present review, by introducing moisture absorption model, performance degeneration of composites under hygrothermal environment was described. Following that, the review focused on the fatigue properties of composites under hygrothermal environment. The hygrothermal factors affecting the fatigue performance of fiber reinforced polymer composites were reviewed. The challenges and the existing problems were summarized. The future development of fiber reinforced polymer composites was finally discussed.