The basic principle of light-sectioning method(LSM) is described in this paper.On the basis of analyzing the features of several common methods used in acquiring light-trap center,in view of the condition that intensity distribution of light-trap is not accord with Gausses function completely,a new improved barycenter method is presented.This method strengthens the weightiness of the point whose light intensity is high,increases the measuring accuracy.We compared it with several existing subpixel level methods used in acquiring light-trap center.The experimental results show that the curve is more smoother,and the 3-D solid rebuilding effect is very good.