In order to solve the problem of poor mirror polishing effect of steel used in plastic die， the polishing efficiency of die steel is improved by optimizing smelting process. The results showed that the mirror effect

was closely related to the purity of steel. From the electric arc furnace burden structure， deoxidization system， LF refining furnace argon blowing control， high vacuum degree cycle of VD vacuum furnace and mold casting process optimization， more comprehensive improvement measures were taken， that is， increasing the use of DRI， using silicon predeoxygenation， optimizing the argon blowing control of steel ladle bottom and improving the high vacuum cycle of VD.The effective size of inclusions decreased from 27.93 μm to 23.65 μm before optimization. The number density of inclusions decreased from 256 / cm

2

to 176 / cm

2

， and the number density of inclusions decreased by 31.2%. The total amount of B and DS and TiN inclusions was controlled， and the customer satisfaction of polishing performance was recognized.