The effects of different properties of mold slag on the surface quality of continuous casting ingots （390 mm × 510 mm） during the continuous casting of 38CrMoAl steel with an Al content of 0.7% to 1.1% were experimentally studied. The results show that the surface quality of 38CrMoAl steel is closely related to the physical and chemical properties of the mold slag. Specifically， mold slag with low basicity， low melting point， and low viscosity having a basicity of 0.38， a melting point of 1 008 ℃， and a viscosity of 0.45 Pa·s can significantly improve the stability of 38CrMoAl steel during the casting process and enhance the surface quality of the ingot. The maximum number of pits on the surface of the continuous casting ingot was reduced from 6.45 per piece to 0.3 per piece， and the maximum number of continuous casting furnaces was increased from 5 to 12. At the same time， the consumption of this mold slag during the casting process was the highest， at 0.45 kg/t； the composition change was the smallest after casting， with the Al

2

O

3

content in the slag at 17.8% and the SiO

2

content at 29.0%.