Abstract: Fe-based gradient cladding layer composed of working layer and M2 transition layer was cladded on 45 steel by tungsten argon arc cladding technique. The microstructure, thermal expansion property, microhardness, residual stress and thermal shock resistance of the gradient cladding layer were investigated, and compared with those of the single cladding layer. The results show that compared with the single cladding layer, the structure of the gradient cladding layer was compact with no hole. The cross section hardness of single cladding layer suddenly decreased when it was 2 mm from the surface, and the cross section hardness of gradient layer suddenly decreased from surface to matrix. The matching degree of thermal expansion coefficient of the gradient layer was better, and the cross section residual stress was lower; also, the thermal shock resistance was better.