Abstract: Laser cladding technology and 35 Cr2Ni4MoA powder were used to prepare the cladding layer on the forged and annealed 35 Cr2Ni4MoA substrate. By observing and analyzing the macroscopic morphology and cross-sectional morphology of the single-pass cladding layer under different laser cladding process parameters, the influence of key laser cladding process parameters on the microstructure and morphology of the 35 Cr2Ni4MoA cladding layer was studied, and it is found that the powder feeding speed has the greatest impact on the width to height ratio of the cladding layer. Then, the effects of the three heat treatment methods of low temperature heat treatment, tempering, quenching and tempering on the microstructure and properties of the cladding samples were studied. The micromorphology, microstructure, tensile strength,hardness and impact toughness of the matrix, cladding layer and heat-affected zone under the three heat treatment conditions were compared in detail. After low-temperature heat treatment, the structure of the matrix is annealed ferrite and pearlite, the structure of the heat-affected zone is ferrite and martensite, and the structure of the cladding layer is martensite. The heat treatment does not change the structure and has a tiny impact on the performance. When only tempering is performed, the martensite in the heat-affected zone and the cladding layer transforms into tempered sorbite, which reduces the hardness of the cladding layer and improves the impact toughness. When quenching and tempering are performed, the microstructure of the cladding layer and the matrix transforms into tempered sorbite. At this time, the tensile strength is the maximum, but the impact toughness is the minimum, which is lower than that of the tempered matrix.