In order to realize real-time seam tracking while changing welding torch′s gesture,a novel tracking strategy based on absolute seam trajectory is proposed.The line structured laser sensor is mounted on the flange of robot in the front of the welding torch.During the welding process,the laser sensor continuously collects the seam position in sensor coordinate system.Using hand-eye matrix and robot position and gesture matrix,the homogeneous coordinate value can be transformed from sensor coordinate system into robot base coordinate system,which formed the absolute seam trajectory;the position deviation can be computed according to the current position of the welding torch and the absolute seam trajectory.In order to improve the accuracy of the calculation,a method of interpolation based on cubic non-uniform rational B-splines is addressed;finally,the position deviation is transformed to the coordinate system of welding torch tool for real-time position correction.The experimental results show that the novel strategy can realize the continuous smoothly tracking while changing torch′s gesture in welding process,and its tracking error is better than 0.5 mm which satisfies the requirements of automatic welding.