Abstract: In order to study the influence of heat input on laser welding quality of 304 austenitic stainless steel, experiments were carried out by using high power Nd:YAG laser and welding robots. Weld appearance, microhardness and mechanical properties were analyzed with an optical microscope, a microhardness tester and a tensile testing machine. Experimental results show that heat input has great influence on weld appearance, microhardness and mechanical properties. Furthermore microhardness is different in different areas. The lowest tensile strength values of laser welding are 671.67MPa at low laser power and 780MPa at high laser power.