304 stainless steel joints with 5 mm thick are welded by laser-MIG hybrid welding with 10 kW disc laser. The influence of the laser-arc distance on the forming and mechanical properties of the welding seam is investigated, and the influence mechanism of the arc on microstructure and microhardness of the welding seam is analyzed. The results show that an optimized laser-arc distance not only have a synergistic effect between the laser heat source and the arc heat source, but also increases the stability of the droplet transfer. When the laser-arc distance is 1 mm, which makes an optimized distance, the droplet transition is stable and the welding seam is formed well. The tensile strength is 631.33 MPa, which is reaching to 98.6% of the strength of base metal. The microstructure of the welding seam is composed of austenite and skeletal and lath ferrites, and the microstructure of the upper part (Ⅰpart) of the welding seam is smaller than that of the middle part (Ⅱpart) and lower part (Ⅲ part) of the welding seam. The microhardness for the upper part of the welding seam is about 175 HV, which is equivalent to that of the base metal, the microhardness for the middle part of the welding seam is about 180 HV, and the microhardness for the lower part of the welding seam is about 190 HV, which are all lower than that of the heat affected zone.