In order to investigate the influence factors of the fiber welding modes for 301 stainless steel, a group of experiments with the laser power, welding speed and defocus distance as the variables arc designed in accordance with the idea of an uniform experimental design. By the analysis of the formed welds, the characteristic forms of the heat-conduction welding and the deep -penetration welding arc obtained in the fiber laser welding process. The relationships among the weld mode, each welding parameter and their interactive action arc calculated quantitatively, and the influence factors of the welding modes arc determined. The results show that, there arc four typical weld formation forms determined by the heat input density for the 301 stainless steel fiber laser welding. The weld has an arc shape when the heat input density is smaller than 13. 01 J " mm -3 and the corresponding welding mode is the heat-conduction welding. When the heat input density is larger than 66.82 J"mm-3, the weld has a nail head or a nail shape and the corresponding welding mode is the deep -penetration welding. Meanwhile, there exists an intermediate mode when the heat input density is between the two values for the above welding modes.
