The Steger algorithm will produce a mass of redundant points when extracting the center line of laser fringe, a method of multi-line structured light center extraction based on improved Steger algorithm was proposed. First, the global thresholding method was used to extract the laser fringe region effectively, and the Steger algorithm was used to preliminarily obtain the center line of laser fringe. Second, the noise points were filtered out by threshold method and the collinear light fringe lines were fitted by least square method. The distance between the filtered points and the fitted line were calculated, then an appropriate threshold to recover valid laser points was set. Finally, the coordinates of the center points of laser fringe were corrected by fitting straight lines. Experimental results show that compared with Steger algorithm, the proposed method can effectively filter out the noise points and eliminate a large number of redundant points generated by Steger algorithm. When the accuracy value of the corresponding points is less than 1 pixel, the number of the center point of the laser fringe is reduced by 16%. Compared with the Steger algorithm, the difference of standard deviation of the distance between the laser point and the fitting plane after 3D reconstruction by the proposed method is 0.48×10-5 mm. However, the extracted laser line is more flat without redundant and noise points, which is more in line with the requirements of the project.