Aiming at the problem of energy loss in the process of welding at present, a new hybrid welding technique that low powered laser (about 400 W) combined with arc was put forward. Taking magnesium alloys as objects, it was found that the new technique had many advantages such as high welding speed, deep penetration and high quality welded joint comparing with that welded by laser or arc alone. Besides, the mechanical properties of the welded joint were improved remarkably. Comparing with high powered laser (about 2000 W)-arc hybrid welding, the laser used in the new technique was about 400 W, which was about 1/5 of that of the former, so the welding costs could be reduced markedly, while a great deal of energy was saved. In the research of arc behaviors, a new hybrid mechanism was proposed, in which the ability of arc to discharge was improved mainly because the laser pulse acted on the negative arc (electrode was positive and the specimen was negative) during the hybrid welding.