Abstract: The effects of welding parameters including laser power,welding speed,welding conditions on pore formation tendency(represented as porosity) during laser welding of die-cast magnesium alloys with two different gas contents were investigated,and the porosity prevention measures were also studied.It is shown that the pore formation tendency during laser welding of 2 mm thick die-cast magnesium alloys with higher gas content is greater than that of 5 mm thick die-cast magnesium alloys with lower gas content.As a whole,the porosity increases with the increase of laser power and the decrease of welding speed for both two thicknesses.For 5 mm thick die-cast magnesium alloys with lower gas content,low porosity weld bead can be obtained by both double sided welding and remelting after welding,and the porosity can reduce to 2.4% and 2.5%,respectively.However,for the 2 mm thick die-cast magnesium alloys,these porosity prevention measures are not effective.