Abstract: Described in the article are the main aspects concerning the mandrel,a key process tool for cold-rolling of precision seamless steel tube,including the work condition characteristics,material selection and heat treatment.And analyses are also made on the problems concerning the manufacturing process and operation of the GCr15 steel mandrel as well as the material characteristics of the 9CrSi and Cr12MoV steels.As a result,a proper manufacturing process of the said mandrel is proposed in order to solve the chronic technological problem of how to properly control the heat treatment deformation of slim tools like the mandrel in a bid to get both high hardness and high wearability.