Through the tensile testing,bend testing,hardness testing and analysis of the microstructure,this paper studied the conventional mechanical properties and the microstructure of 3 mm ferritic stainless steel welded joints by MAG,CMT,PAW and TIG. The results show that:The conventional mechanical properties of the joints by all these four welding processes are accepted. The austenitic stainless steel welding wires were applied to the MAG,CMT and TIG joints. The microstructure of weld is the lath ferrite or reticulum ferrite in the austenitic matrix,and these joints have higher hardness. The microstructure of autogenous PAW weld is bulk ferrite with homogeneity of the parent material,and its hardness is less than that of the parent material. The coarsening of ferrite grain has an adverse effect on the strength and hardness of the joint.