The laser lap welding experiment with Cu, Pb metal sandwich addition was carried out based on the DC56D+ZF galvanized steel of 1.2 mm thickness and the 6016 aluminum alloy of 1.15 mm thickness. Using optical microscopy, scanning electron microscopy, X-ray diffraction and tensile test, the forming of welding, microstructure, element distribution, fracture morphology and the main phase of the welded joint region and mechanical properties of joints were studied. The results show that when Cu and Pb sandwich is added in steel/aluminum, the average tensile strength and elongation of the steel/aluminum laser welding joints is 49.44 MPa and 1.63% as well as 73.51 MPa and 2.37%, respectively. Compared with that without Cu or Pb sandwich addition, the strength and elongation are improved, and Pb is considered as the best metal sandwich based on improved mechanical properties of joints. Steel and aluminum joint specimen fracture shows a brittle fracture characteristic without metal sandwich, the brittle characteristic is not obvious with Cu metal sandwich, while the ductile characteristic is found with Pb sandwich. When Pb sandwich is added, Fe, Al, Zn, Mg and Pb elements change a lot and the mixing zone width is larger in the transition region of steel/aluminum joints. In addition, a new Mg2Pb intermetallic compound is produced with the better stability, FeAl brittle intermetallic compounds are inhibited, and the mechanical properties of weld metal is improved significantly with Pb sandwich addition