Through arranging coded markers on the blade surface of a wind turbine, and based on binocular stereo imaging principle and image feature matching and tracking method, the spatial motion information of coded markers can be obtained dynamically and in real time. Aiming at the problem of noise pollution affecting modal identification, a singular value decomposition (SVD) and Cadzow algorithm was used to construct a Hankel matrix without noise pollution, which effectively reduces false modals caused by noise. In order to solve the problem that false modes are easy to appear in the process of modal order determination, an improved eigensystem realization algorithm (ERA) is proposed. Compared with the traditional ERA, the proposed method improves the accuracy of natural frequency identification by 3.6% and obtains a clearer stabilization diagram.