Abstract: Spinning mandrel is a key tooling in spinning processing production, mostly made of high alloy tool steel, common materials are 9SiCr, CrWMn and so on.Generally, the spinning core die must be heat treated, and the hardness of the core die must be ensured to reach the range of 58～64HRC to meet the requirements of use. At first,we used the oil-cooled quenching method after the well furnace heating on the CrWMn core mold, so that the final hardness can only reach 50～55HRC or so, which can not meet the use. Finally, through the process improvement,the core mold is made to reach two kinds of hardness zone by the water quenching and oil cooling process, the hardness of the used part reaches 59～60HRC, and the hardness of the shaft journal reaches 35～40 HRC.