Abstract: A method of weld seam measurement based on structured light stereovision is proposed, which employs two charge coupled device cameras and a laser emitter fitted on the end-effector of the robot. A piano-convex cylinder lens is utilized to convert the laser beam to plane, to forms a stripe on the welding works. Two frames of stripe image are captured by the cameras synchronously. Through the position and pose of the end-effector with the parameters of the cameras and the plane, which can be obtained easily using a simple calibration method provided in this paper, three groups of position values in Cartesian space for each point in the stripe can be derived. Then the accurate three-dimension position of the edge points in the weld seam can be obtained from them by using information fusion algorithm. An experiment that V type weld seam is measured and tracked automatically is successfully conducted.