In industrial production, the standoff distance of magnetic pulse welding (MPW) is a critical parameter as it directly affects welding quality. However, the effects of standoff distance on the physical properties of MPW joints have not been investigated. Therefore, in this study, aluminum alloy (AA5182) sheets and high-strength low-alloy steel (HC340LA) sheets were welded through MPW at a discharge energy of 20 kJ, under various standoff distances. Thereafter, mechanical tests were performed on the MPW joints, and the results indicate that there is a significant change in the shear strength of the AA5182/HC340LA-welded joints with respect to the standoff distance. When the standoff distance ranges from 0.8 to 1.4 mm, the strength of the joint is higher than that of the base AA5182 sheet. Microscopic observations were conducted to analyze the interfacial morphology, element diffusion behavior, and microdefects on the welding interface of the AA5182/HC340LA joints. The AA5182/HC340LA joint with a standoff distance of 1.4 mm possesses the longest welded region and the largest interfacial wave. This interfacial wave pattern is suitable for achieving MPW joints with high shear strengths.