Distributed optical fiber composite overhead ground wire (OPGW) health monitoring based on FBG (fiber Bragg grating) sensor has been widely studied. In this paper, a wave prediction method based on cubic spline function fitting is proposed for OPGW galloping cable event. Firstly, the mathematical relation between the phase variation of sensor and the galloping cable wavelength was established through theoretical derivation. Then, the simulation results of the phase shift signal before and after the cubic spline function fitting under ideal galloping condition were analyzed, and the effectiveness of the proposed method was proved. Finally, it was applied to a 220kV line, and the intensity graphs of galloping monitoring in typical weak wind environment and strong wind environment were compared and analyzed. According to the actual monitoring results, the method selected in this paper can effectively improve the signal characteristics of intensity graphs, and it can be concluded that the wavelength within the range is about 200m under strong wind condition, and the wavelength within the range is about 50m under weak wind condition. This method provides technical reference for intelligent monitoring of image recognition of cable galloping events and has strong application prospect.