A carbon fiber reinforced polymer (CFRP) cable has the advantages of high strength, lightweight, and good durability. However, the durability of its anchoring structure in a long-term wet service environment is doubtful. In this study, a CFRP cable was subjected to a 2 million fatigue cycle test with 200-MPa stress amplitude and a stress upper limit of 0.65, the low-end anchor was placed in a water environment, and fiber gratings were attached at both ends of the CFRP tendons to measure changes in the axial strain. The test results show that under cyclic loading, microcracks are generated between the CFRP tendons and the anchoring filler, and the stress redistributes inside the anchor; water accelerates the internal stress of the anchor. The redistribution of stress aggravates the bond fatigue failure. The rule is divided into two stages: the first stage has a higher rate, which is mainly concentrated in the first 500 thousand cycles, and the second stage is from 500 thousand to 2 million cycles. The stress redistribution gradually stabilized. The CFRP cable under study safely passed the fatigue test, but the remaining strength was reduced by 17%, thereby indicating that the impact of the water environment on the durability of the CFRP cable anchoring structure cannot be ignored.