.A rotating mirror high-speed imaging system can capture and track moving targets, obtaining high-resolution images of targets and it is suitable for capturing high-speed moving targets. Therefore, we propose a target velocity measurement method based on a rotating mirror high-speed camera. Since this system is based on monocular camera capture, traditional binocular vision-based visual velocity measurement methods are no longer applicable. We reconstruct the homography matrix of the plane where the target is located, calculate the virtual difference map of the target’s feature points, and reconstruct the three-dimensional (3D) coordinates of the feature points on the moving target. Then, based on calibration data, the actual 3D coordinates of the target are calculated, and the target’s motion speed is calculated using the frame rate of the camera. This method achieves 3D reconstruction of feature points of moving targets solely based on a monocular perspective and is highly suitable for a rotating camera model, allowing for continuous measurement of the motion speed of the target and observation of speed variations, expanding the range of velocity observation for high-speed moving targets. The experiment shows that this method has the advantages of low requirements for the field, simple construction of experimental equipment, and high robustness. It can still measure the speed of the target with high accuracy under relatively simple conditions. The average relative error of displacement measurement experiment using this method is 2.03%, which shows the feasibility and accuracy of this method. We believe it has significant application value for measuring the speed of high-speed moving targets.