The detection of moving object in the scene through calculating the optical flow field is a very important research point in computer vision. The computation accuracy of optical flow field is directly related to the accuracy of target detection. In view of the fact that the optical flow field of motion target is not prominent in the whole optical flow field due to the dynamic background,a new method based on blocked integral projection registration algorithm is proposed. Firstly,the motion parameters of the image background are obtained by the proposed blocked projection-based registration algorithm. Then the motion compensation of the background is carried out. After that,the optical flow field in the effective area of the image is obtained by using the traditional L-K algorithm. The algorithm is verified by a real video sequence,and the results compared with the results of the classical L-K algorithm. The comparison results show that the moving targets in the optical flow field obtained using the proposed algorithm is more prominent,and the algorithm is effective.