In order to improve the water erosion resistance property of the 17-4PH stainless steel, Stellite6 alloy coating is prepared on the surface of 17-4PH stainless steel by laser cladding. The coating microstructure, phase composition and element diffusion are studied and the hardness distribution and water erosion resistance property of the coating are analyzed. The results show that the microstructure of the Stellite6 coating is composed of plane crystal, cellular and columnar crystal, dendrite, and equiaxed crystal. The phase consists of γ-Co solid solution with face centered cubic (FCC) structure, M23C6, Cr7C3, and CoCx. Fe and Co elements diffuse between the substrate and the coating layer obviously. The highest hardness of the Stellite6 coating is 561 HV, and its average hardness is about 1.4 times of that of the substrate. In the multi-channel and multi-layer cladding, softening phenomenon occurs in the overlapped regions and the transverse hardness of Stellite6 coating fluctuates periodically. Under the conditions of pressure being 80 Mpa, temperature being 80 ℃ and water erosion time being 30 h, the substrate surface is destroyed seriously. However, the Stellite6 coating surface basically retains the original appearance. It indicates that the water erosion resistance property of the coating has been significantly improved than that of the substrate.