Abstract: Aiming at curved seam tracking with large curvature that wheeled welding mobile robot encountered in shipbuilding and large spherical tank welding, a method of dynamic tangent to weld seam is proposed on the basis of real-time wavelet denoising method and weld seam tangent, with combination of sliding-mode variable control. The mathematic model based on the method is established, the simulation performed at MATLAB and welding experiment were carried out to verify this model. The experiment and simulation results indicate that this method can perform real-time speed correction for welding vehicle with fixed step, keeping the welding torch moving with constant tangential velocity along seam trajectory, and thus it guarantees the welding quality and achieves real-time automatic curved seam tracking. It provides a new theoretical thought for the application of wheeled welding mobile robot in automatic seam tracking with complicated trajectory.