In the light-sectioning method,it is difficult to accurately extract light-knife center contour due to those influences such as sun light,surface texture information and the low reflection of measured object,So an effective solution to eliminate those influences is presented.By controlling the laser,two consecutive images in which only one image contains laser information are acquired.Then,the background motion compensation is processed to make the two images have slightly difference only in the laser location,thereby the laser trace is emerged after image subtraction.Finally,a complete light-knife center contour is obtained through refinement and repair for data.The experimental results show that proposed method is effective to eliminate the influences mentioned above and it is adapted for measuring 3D shape of the mobile objects in a measuring locale.