In order to solve the fatigue problem of offshore floating photovoltaic direct current(DC) cable between floating blocks under the influence of wave motion, this paper proposes a method to evaluate the fatigue life of DC cable. On the basis of analyzing the fatigue damage mechanism of the DC cable, usingthe service life of the DC cable is accurately predicted by using the stress prediction method with the COMSOL finite element simulation software. By simulating stress conditions under different working conditions, the results show that: The fatigue life of DC cable across floating blocks is negatively correlated with the maximum equivalent stress, and the life decreases with the increase of displacement degree. The dangerous point of cable fatigue is near the fixed point at both ends of the cable. At the same time, the influence of different suspension lengths on the cable fatigue life is analyzed by simulation. The simulation results provide a useful design reference for optimizing cable layout and improving its service life.