Abstract: Low alloy steel was cladded on 304L stainless steel matrix by using arc increasing technology, the composite structure of stainless steel and low alloy steel was prepared, and the forming structure and hardness distribution of the cladding layer were analyzed. It is found that the top layer is columnar crystal, the middle layer region is composed of coarse crystal region and fine crystal region, and the bottom area of the cladding layer is mainly equiaxed crystal structure. Solidification transition layer is formed at the interface between the cladding layer and 304L matrix. Due to diffusion of elements, a large number of dendritic ferrite is formed on the austenite matrix at the 304L side near the transition layer. Through the hardness analysis, it is concluded that from the cladding layer to the matrix, the hardness value increases first and then decreases. The hardness of solidification transition layer at the interface between the cladding layer and 304L matrix reaches the highest. The hardness of both sides of solidification transition layer is different from that of the transition layer, which is unfavorable to mechanical properties.