Abstract: YAG pulse laser welding of thin AZ61 magnesium alloy sheets was conducted.The microstructure and chemical compositions of the welded joint were examined with optical microscope(OM) and energy dispersive X-ray analysis(EDX), and the microhardness and tensile strength of the joints were measured.The results show that the weld front side slightly collapsed but the weld back side shaped well.The weld had good appearance and solid mechanical properties.The grain was finer and the microhardness was higher in the fusion zone than that in the base metal.The tensile strength of the joint was 250 MPa, equivalent to that of the base metal.The evaporation of Mg led to the increasing of Al content in the weld, but the Zn content was low.