Aimed at seam tracking of fillet weld for robotic welding,we developed laser vision sensor and filter system in this paper. Based on measuring principle of matrix transformation,it simplified calibration of vision system. Steger method based on Hessian matrix is used to extract sub-pixel level linear feature and its orientation information. The random sample consensus algorithm is used to fitting lines as profile model and center of weld seam is extracted furtherly. Tracking test results shows that mean tracking error is 0.52 along welding direction,which meets the actual welding production requirements of the robot.