Moving object detection which is an important part of the digital image processing technology is research focus and difficulty in computer vision, pattern recognition, object recognition and tracking, moving image coding, security monitoring and other fields. It also has a wide application prospect in the military, national defense and industry fields. However, when there are large amount of moving targets and exercise conditions, the amount of data generated is also inestimable and target detection is a bottleneck in the data processing at the same time. The work of this paper is to simplify motion detection in optical flow constraint equation solving process and all the solving processes were constructed on GPU for fast speed, then it forms a fast moving target detection.