The laser welding test with Sn-5%Zr (mass fraction) powder addition is carried out on the DP590 dual phase steel with thickness of 1.4 mm and the 6016 aluminum alloy with thickness of 1.2 mm. By using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), electron backscatter diffraction (EBCD) and tensile test, the effect of Sn-5%Zr powder addition on the microstructure, fracture morphology, main phase, content and distribution of phase, grain size and mechanical properties of joints are studied. Elastic moduli are calculated by using first-principle method based on density functional theory for FeSn, Fe3Sn, Fe3Al, FeAl and Fe2Al5 compounds. The results indicate that the average shear strength of the welding sample with Sn- 5% Zr powder reaches 37.90 MPa. Compared with that without Sn-5%Zr powder addition,the average shear strength of welded joint increases. Because of the formation of ZrAl3 compounds, it promotes the refined grain size of Fe- Al intermetallic compound in aluminum/steel interface, Al spreads to the molten pool is inhibited by Sn, the thickness of Fe-Al intermetallic compound layer is reduced, FeSn and Fe3Sn intermetallic compounds have better ductility, the proportion to brittleness and ductility phases of the interface layer Fe-Al intermetallic compounds are changed, the weld width and bonding rate effectively increased, which can improve the mechanical properties of weld joint with Sn-5%Zr powder addition.