Magnesium and its alloys are the lightest among the metallic materials which are in common use, having a high strength-to-weight ratio along with an excellent machinability and a high damping capacity. Because of these characteristics, nowadays they are applied to various structural parts such as aircraft, automobiles, optical and electronic instruments, industrial robot components. TIG welded joints of AZ31 magnesium alloy has high joint efficiency which can be obtained by the selection of optimum welding conditions. If the welded joints of magnesium alloy are applied to the structure materials, it is very important not only the strength of under static load but also the strength of under dynamic load. However, there is only few report about impact properties of welded AZ31 magnesium alloy joints. In this research, AZ31 magnesium alloy plates 6 mm in thickness were welded on butt welding of square groove without root gap and filler wire using TIG welding process. AZ31 magnesium alloy was carried out at various welding conditions. The effects of welding conditions and notch location on impact properties were studied. Impact values of welded joints were nearly equal to those of the base metal, regardless of welding current. In case of the notched specimens of welded joints, crack initiation energy showed slightly lower than crack propagation energy, regardless of notch location. But, unnotched specimens of welded joints, crack initiation energy showed remarkably high value than crack propagation energy. This means, crack initiation energy spent the large amount of total absorbed energy.