After focusing the laser beam, a small spot can be obtained that can be precisely positioned and used in group welding of micro and small work pieces for mass production. Mainly for welding thin-walled materials and precision parts, it can realize spot welding, butt welding, bonding, sealing welding, etc., high aspect ratio, small weld width, small heat affected zone, small deformation, high welding speed, no need to process after welding or simply process.