A new wind turbine blade damage detection method is proposed to address the challenges surrounding imprecise positioning and the inability to monitor the turbine under operating conditions, which is a shortcoming of traditional wind turbine blade damage detection. The proposed method uses optical frequency domain reflectometry(OFDR) to measure the surface strain of the wind turbine blade. Subsequently, fast Fourier transform is taken for the strain value and its fundamental frequency amplitude is taken to obtain the blade surface strain distribution. On this basis, the position, length and width of the blade damage are calculated. According to the relationship between the strain and damage degree, the damage degree judgment formula is fitted, and the blade damage degree is identified. Based on OFDR, a cantilever beam damage detection experiment is designed to simulate the instantaneous state of the cantilever beam vibration, and the damage location is identified according to the strain distribution, which verifies the feasibility of the proposed damage identification method.