The effects of Zn content on the microstructure, porosity, hardness and interfacial bonding strength between coating and substrate were studied. Pure Al and Al-Zn composite coatings with excellent properties were prepared on Q345R plate by cold spraying technology, the morphology of the coating was analyzed by scanning electron microscope, the mechanical properties of the coating were characterized by Vickers microhardness tester, and the interface bonding mechanism between the coating and the substrate was revealed.The results show that the bonding between pure Al and Al-Zn composite coatings with Q345R steel substrate is well, without obvious holes and cracks at the interface. With the increase of Zn content, the density and hardness of the composite coating increase gradually, and the interfacial bonding strength of pure Al and Al-20wt.%Zn composite coating is similar, and the failure fracture mode is typical interfacial adhesive fracture. With the increase of the Zn content, the interfacial bonding strength between the coating and the substrate increases gradually, the bonding strength of Al-40wt.% Zn composite coating is 35 MPa, and the fracture mode changes from adhesive fracture to the mixed failure mode of dominant interfacial adhesive fracture and auxiliary cohesive fracture of the coating. In conclusion, cold spraying, characterized by low temperature solid state deposition, can effectively avoid the adverse effects such as oxidation, phase transition, and thermal cracking caused by high temperature. In the deposition process, with the increase of the Zn content, the tamping effect on the coating is constantly strengthened, which improves the compactness and the mechanical properties of the coating.