Abstract: Fatigue failure and stress damage are the main damage forms of marine risers. To study the variation rule of surface magnetic field signals of X80 steel during tensile fatigue process under geomagnetic excitation, the fatigue tensile test of X80 steel specimens under typical working conditions was carried out with an MTS810 250 fatigue tensile testing machine. During the experiment, the variation of magnetic field on the surface of the tensile specimen was monitored by a magnetic memory sensor, the fatigue failure of the specimen was observed by a handheld microscope, and the morphology of the fracture was analyzed with the help of scanning electron microscope(SEM). The results show that the magnetic memory is sensitive to the tensile fatigue damage. Thus, the characteristic parameters of magnetic memory detection for tensile fatigue damage of X80 steel were proposed, which took the extreme value of magnetic memory signal with background removed H_E(X) and the line slope of the extreme value of tangential gradient signal S_K(X) as the eigenvalues. As a result, zero crossing phenomena occur to H_E(X) and S_K(X) in the stage of crack initiation. The acceleration of H_E(X) and S_K(X) speeds up with the increase of the fatigue cycle, which is consistent with the crack growth law during the fatigue process. Generally, H_E(X) and S_K(X)can reflect the fatigue failure process of the specimen, and they can be used to monitor the fatigue damage of marine risers. This research results could provide a reference for the field application of the magnetic memory detection method in the fatigue damage detection of marine risers.