The light soldering machine replaces the fixed light path before, and it is flexible and convenient to weld by hand. The welding distance is longer, overcoming the limitations of the workspace, and it can not be used automatically when the workpiece size is not uniform. It is mainly used for welding large workpieces, fixed positions such as inner right angle, outer right angle, plane weld, small heat affected area, small deformation, large welding depth and firm welding. It is a new and flexible welding process for long-distance welding of large workpieces.