In order to study the effect of shielding gas on mechanical properties of austenitic stainless steel welding joint, a comparison between weld with shielding gas and weld with no shielding gas in the same line energy is studied. Austenitic stainless steel in 0.7 mm thick is welded by using Nd:YAG laser, the microstructure and mechanical properties of the welding joint are analyzed by means of scanning electron microscope (SEM), micro- hardness tester and material testing machine. Results show that two types of welding both achieve full penetration, and have good weld- forming in the same laser processing parameters. When welding with no shielding gas, with the decrease of welding speed, the tensile strength of welded joints also decrease. The decrease rate reaches 20% at most. After adding shielding gas, the tensile strength of welded joints changes smoothly, all tensile strength are over 90% of matrix.