A method of motion trajectory detection is proposed in this paper, including image segmentation and perspective transformation. First of all, the video images are processed. Then the images are dealed with Grayscale, Binarization and Connected Component Labeling. The contour of images are acquired with Canny edge detection algorithm, and the coordinates of contour pixel are obtained with the MATLAB programming. Finally, the actual coordinates of the video images are obtained with Perspective Transformation. And shadow motion trajectory is simulated in the two-dimensional and three-dimensional coordinate system.