Abstract: In order to improve the hardness of the coating and reduce the crack, ultrasonic vibration can be applied to the laser coating technology. The nickel-based powder cladding layer is prepared on the surface of 45 steel, the formation and the solidification of the molten pool are influenced by the ultrasonic vibration, and the surface flatness, microstructure and microhardness of the cladding layer are used as the basis for evaluating the quality of the cladding layer. The results show that,by adding ultrasonic vibration in the process of laser coating, the coating layer with small surface fluctuation, no obvious unmelted metal powder particles and no obvious defects such as cracks and pores can be obtained. The microstructure of the coating is fine and the size when ultrasonic vibration is applied, is uniform. The microhardness of 750 HV at the top of the coating without ultrasonic vibration is increased to 900 HV, which improves the surface smoothness of the coating. Adding ultrasonic vibration to the process of laser coating can optimize the solidification process of the molten pool and play an important role in grain refinement and homogenization. It is an effective method to improve the quality of the coating.