The invention relates to a CO2 (carbon dioxide) gas shielded welding method for flux-cored wires of a marine engineering lifting pile leg, which includes the steps: firstly, selecting a welding material and gas; secondly, treating a welding control point by cleaning up oil, rust, oxide and other impurities within the range of 20-30mm on the periphery of a preweld groove; thirdly, performing electric preheating, adjusting welding parameters, adjusting welding according to corresponding WPS (welding procedure specification) welding parameters, and immediately performing post-weld heat treatment after welding; and fourthly, during multilayer and multipass welding, strictly controlling energy of each welding line below 1.5KJ/mm, adopting low-current unswing welding, leading the preheating temperature of a first pass not to exceed the lowest preheating temperature of 15 DEG C, and leading post-weld deformation not to exceed 5 degrees. The CO2 gas shielded welding method has the advantages of arc stability, less splashing, easiness in slag detachability, weld pass attractiveness and nondestructive flaw detection qualification rate reaching more than 95%.