Abstract: The effecs of different welding processes on the welding quality of 3 mm-thick high strength marine steel sheet was investigated. The results show that the 3 mm-thick test sheet is saddle-shaped after different welding processes. The test sheets by electrode arc welding and manual gas shielded welding are seriously deformed, and the differences of deformation and residual stresses of the above sheets are almost the same. There is a slag inclusion defect in the seam of flux cored wire CMT(cold metal transfer) automatic welding sheet. With solid wire CMT automatic welding, the welding seam of the test sheet is uniform and has no internal defects, the residual stress in the center of the welding seam is obviously reduced, the average deformation is 37.8% less than that of the electrode arc welding, and the energy input is only 22.4% of that of the electrode arc welding. The variation trend of welding deformation of the test sheet is consistent with the energy input.