This paper put forward laser welding technology with Ti–foil in an overlap magnesium-on-aluminum configuration, then, AZ31 magnesium alloy and 6061 aluminum alloy was welded, finally micro-structure and properties of Mg/Al fusion welded joints under the interaction of titanium foil-laser was studied. The results shows that adding Ti–foil can realize the effective connection of Mg/Al, and the shear strength (line strength) of Mg/Al joint can reach 58 N/mm. The morphology of molten pool changes from“ V” shape without Ti–foil to“ goblet shape” with Ti–foil. As the thickness of Ti–foil increases, the melt pool of joint increases, and Ti–foil melts close to the matrix of aluminum side. Ti element is distributed in the molten pool along with the pool flow field, which leads to the forming of Ti₃Al compound. The addition of Ti–foil can inhibit the direct contact between magnesium and aluminum, avoiding the formation of brittle Mg/Al compounds through the reaction between Mg and Al. The addition of Ti–foil has a certain barrier effect. However, the thermal conductivity of Ti–foil is relatively low, and far away from the laser heat source, Ti–foil is not completely melted. Therefore, the combination of Ti–foil and base material still needs to be improved.