The center overlap welding experiments of aluminum alloy and magnesium alloy sheets are carried out by the nanosecond laser technology, and the effects of nanosecond laser process parameters on the formation and mechanical property of Al/Mg welds are analyzed. The results show that the Al/Mg joints are successfully welded by the nanosecond laser and their shear tensile strength can reach to 86 MPa under the conditions of low energy input, high power density and high welding speed. In the laser power range of 5-10 kW, the penetration depth of welds possesses a linear relationship with the nanosecond laser power density, however a logarithmic relationship with the laser duration and the laser point energy.