Abstract: For extracting the weld seam feature lines in line structured light stripe, a slope analysis method based on linear fitting is proposed. In this method, all the n pixels in the light stripe are arranged in the order of the coordinates, progressive from the starting point, linear fittings are performed for each consecutive points, and total n0 values of the slope are recorded. The number distribution of the points in each stripe line is calculated by the change characteristics of the slope and point set division is completed. According to the division of the point set, linear fitting are performed and these fitted lines are taken as the weld seam feature lines. Finally, the influence of parameter n0 on the fitting lines is discussed. The experiment results indicate that this method can efficiently extract the feature lines in corner butt welding, overlap butt welding and V-groove welding seam and meets actual field requirements.