Abstract: The effect of preheating temperature on U75V laser cladding forming was studied, and the microstructure and hardness distribution of the cladding layer were analyzed. The results showed that when the preheating temperature was lower than 125^\circ \mathrmC, the cladding layer appeared the defects of holes and uneven distribution of penetration depth, and the overall size fluctuated greatly. The multilayer cladding layer preheated at 125^\circ \mathrmC had no obvious defects. After the base material was preheated, the microstructure of the cladding zone in the single-layer cladding layer changed from Widmanstatten to lower bainite, and the heat-affected zone was mainly coarse-grained martensite with little change in hardness. The microstructure of the cladding zone in the multilayer cladding layer was columnar crystals and equiaxed crystals, and the martensite in the heat-affected zone distributed in the area near the fusion line. The hardness of the cladding layer decreased after preheating, and the preheating had little effect on the martensite transformation.