Abstract: Effects of laser power,defocusing amount,heat source sequence,heat source distance,heat source arrangement,welding speed and welding current on formation of weld by high-power laser-MAG hybrid welding were studied systematically with the method of plate surfacing. The results showed that the effect of defocusing amount on formation of weld was more significant with the higher laser power under the condition of lower current. The defocusing amount had little influence on formation of weld when the laser power was at 10 kW,while formation of weld surface was better with negative defocusing amount when the laser power increased to 20 kW. The influence of heat source sequence and heat source distance on formation of weld was also significant. Under the condition of negative defocusing amount,better formation of weld was obtained with arc-leading and larger heat source spacing. When using laser-leading and smaller heat source space,more spatter generated and the weld uniformity was poor. But better weld was obtained by significantly increasing the welding current. Using negative defocusing amount and arc-leading was more helpful to increase weld penetration.