According to the characteristics of laser spot,a method for detecting the center position of laser spot is proposed. First,the center position of the laser spot is assumed. Then,it is reconstructed by the principle of equivalent intensity on projection circle of the assumed center point of the laser spot. And then,the absolute sum of the intensity difference between the two before and after the reconstruction of the laser spot is used as an index to evaluate the distance between the assumed point and the center of real spot. Finally,the index minimization principle is used to obtain the center position of laser spot. The theoretical analysis shows that for the standard Gauss distribution laser spot,the evaluation index is proportional to the distance between the hypothetical point and the real spot center,and the evaluation index value is zero at the real spot center. For the actual laser spot,the value of the evaluation index at its center is close to zero. In order to improve its anti-noise ability,the distance weighting method is used as the improved evaluation index. The results of the study example with noise interference show that the accuracy of sub-pixel center location is better than 0.1 pixels;the proposed method is of high accuracy,fast operation,good stability and strong anti-noise ability.