Laser wire filling welding method is used with different welding parameters and welding environments by using16 mm thick 921 A marine steel as the base metal. The metallographic analysis and mechanical property test are carried out for the weld. The influence of the main welding parameters such as laser defocusing distance,wet water depth,environm-ental pressure and welding speed on the welding quality are studied. The results show that the depth and width of penetration reduce gradually as the environmental pressure increases,and the weld height decreases slightly as the pressure increase.When the water depth is within 4 mm,the weld is relatively smooth without obvious appearance defects;when the water depth increases to 5 mm,the uniformity of the weld becomes poor;when the water depth increases to 7 mm,the weld is difficult to form,and there are only burn marks on the surface of the base metal. The width of penetration decreases first and then stabilizes gradually as the defocusing distance increases.The depth of penetration reduces gradually as the defocusing distance increases. The appearance of weld is best when defocusing distance is about 20 mm.