The precise location of the laser spot center is an important step to raise the measurement resolution in large 3-D surface profile measuring system of laser scanning. While measured distance is large, laser spot intensity distributes non-uniformly so that the deviation between the geometric center and the intensive center of the spot emerges because of the influence of various factors. The conventional methods of locating center of spot is unsuitable to the condition. According to the feature that the better part of circle spot can be obtained by the image of spot, a new method for locating the center of spot based on Hough transform (HT) is presented. The experimental results show that the method can effectively increase the measuring precision of large scale 3-D surface profile.