Abstract: Martensitic stainless steel coating was deposited on the surface of low-alloy high-strength steel Q355D with high-speed laser cladding technology, and the effects of process parameters on the phase structure and microhardness of the cladding layer were investigated. X-ray diffractometer (XRD), scanning electron microscope(SEM) and electron backscattering diffraction (EBSD) were used to analyze the phase composition, microstructure and elemental distribution of the coatings. The results show that, the coatings with the thickness of 500 -1000 μm can be deposited through the control of the process parameters, with no obvious cracks, pores and other defects, and the coatings have good metallurgical bonding with the substrate. The coatings in different parameters are both composed of martensite, austenite, and carbides, and the hardness of the coating can reach 2.85 times than that of the substrate. However, the heat input can affect the precipitation of the carbides and the performance of the coating. The coating with low heat input has finer grains and more uniform composition distribution, but the carbide precipitation gets suppressed, and the hardness of the coating decreases.