Abstract: The time-domain vibration displacement video of the structure was captured by a high-speed camera, establish the pixel intensity field of its grayscale image based on video frame-by-frame image information and extract the phase information. The optical flow equation and solution method are defined Based on optical flow algorithm and image phase information, calculat the instantaneous velocity field of each pixel in the image at different time is to obtain the time-domain vibration information. Considering the problem that only the structural motion information can be obtained but the excitation signal cannot be measured in image progress, the singular value decomposition algorithm is used to achieve the purpose of modal separation and vibration modal information extraction. The vibration modal information obtained by the proposed method has the advantage of high spatial resolution, and the effectiveness of the proposed method is verified by experiments compared with traditional vibration measurement methods,