This study proposes laser-induced arc hybrid welding technology for 6061 aluminum (Al) alloy/DP980 high-strength steel lap jointing with a nickel (Ni) interlayer, which achieves a good connection between 6061 Al alloy and DP980 high-strength steel. The effect of Ni interlayer on the mechanical properties and microstructure of the lap joints and the effect of the Ni interlayer in the welding process are analyzed. An optical microscope, a scanning electron microscope, an electron probe, and an X-ray diffractometer are used to analyze the microstructure and elemental distributions of typical lap joints. Experimental results show that adding a Ni interlayer between Al alloy and high-strength steel can effectively prevent the diffusion of Fe element into aluminum alloy matrix and change the types and distributions of intermetallic compounds (IMCs) at the 6061/DP980 interface. With the Ni interlayer, the IMC-layer thickness reduces obviously, and the IMC layer primarily contains FeAl3 and Fe2Al5. Simultaneously, the Ni element is mainly diffused in the form of an Al-Ni compound and an Fe (Ni) solid solution in the weld. The shear tensile load of the joint with the Ni interlayer can reach a maximum of 173 N/mm, indicating an increase of ~35% compared to that of the joint without the Ni interlayer.