Abstract: Although the 2-roll rotary hot-piercing mill has the advantage of cost effectiveness when making the duplex stainless steel shell, due to its severe deformation during the operation, very high thermoplasticity of the round billet is required.Addressing the S32750 super duplex stainless steel round billet, the Gleeble 1500 thermal simulator is used to carry out the high-temperature tensile test, having got the reduction of the cross-sectional area and the change law of the tensile strength of the steel at different temperatures.The fracture morphology is analyzed with the SEM, and the ferrite contents of the steel at different temperatures are also measured, and then compared with the theoretical values of the ferrite contents as calculated by relevant thermodynamic software.As a result, it is identified that when the ferrite content of the S32750 steel billet is controlled within the range of 60%~70%at a high temperature, it presents the best thermoplasticity, which provides a basis for smooth hot-piercing of the said billet.