Abstract: The double-linked gears in automobile gear-box have been welded with high power CO2 laser;several primary parameters affected welding quality have been analyzed;the welded products were analyzed and tested.The appearance of welding seam was perfect without hollow and welding bead.The ratio between depth and width exceeded 2:1;the hot influenced zone is narrow,the molten zone is compact without bug and the micro-hard reaches 450HV which is higher than raw materials. The gears didn't craze by 15kNm tortile test.