The two materials, steel and aluminum, are difficult to weld because of the large differences in physical properties and chemical composition, resulting in steel and aluminum welding becoming difficult. To obtain high-quality steel/aluminum joints, seven laser scanning paths were used to perform lap joint spot welding experiments on two metals, DP780 duplex steel and 5083 aluminum alloy. The effects of the laser scanning path on the macroscopic morphology, metallographic organization, microhardness and shear strength of the steel/aluminum joint were studied. The results show that the change in scanning path has a greater impact on the joint compared to conventional welding. Swing welding joints have better joint quality and better weld surface formation. Steel/aluminum joints are mainly composed of martensite and ferrite. The use of laser swing spot welding joints with obvious grain boundaries, a small amount of lamellar pearlite at the junction of martensite and ferrite, and there is no significant difference in the grain types of the weld, so the mechanical properties of all parts of the weld are the same, reducing the stress concentration phenomenon after the force is applied. The mechanical properties of the swing spot welded steel/aluminum joint are enhanced, the maximum microhardness of the steel side joint can reach 450 HV, 1.06 times that of conventional, and the shear strength is 83 N/mm, 2.12 times that of conventional welding.