Abstract: The 42CrMo continuous casting roller was surfacing with one layer of 430 alloy and two layers of 414N alloy by submerged arc overlay welding process. By composition analysis, microstructure observation and Vickers hardness measurement of the welding layer, the dilution ratio and burning loss rate of the alloy elements were calculated, and the relationship between microstructure evolution, alloy composition distribution and hardness of welding layer on the continuous casting roller was studied. The results show that the dilution ratio of alloy 430, the first layer of 414N alloy wire and the second layer of 414N alloy wire is 27.3%, 22.3% and 12.5% respectively, and the burning loss rate of Cr element is 1.17%, 1.55% and 0.82%, respectively. From the heart to the surface, the structure of overlay welded 42CrMo continuous casting roller can be divided into 42CrMo matrix, heat affected zone, transition layer, 430 welding layer, 414N inner layer and 414N outer layer. After multi-layer surfacing, a hard surface layer with a thickness of about 3 mm, moderate composition and uniform hardness can be obtained, and the microstructure of the hard surface layer is fine lath martensite.