Abstract: A new method was proposed to measure the welding deformatioin of the butt-welding joints by using the noncontact three-dimensional laser scanner. The steel balls were placed onto the drilled holes for the purpose of accurate positioning. Before and after welding experiment, the butt-welding joints and steel ball were scanned by the laser scanner to gain the corresponding point cloud files. After being analyzed by the imageware software, the final three dimensional coordinates of the steel balls on surface of the plate would be obtained. Results indicated that this method could solve the difficult positioning problem because of high temperature, which might calculate the angular distortion and deflection deformation during welding process. It also contributed to understand the mechanism of welding deformation and realize the accurate positioning.