According to the research on the deformation resistance and the ferrite transformation behavior of X80 pipeline steel by using Gleeble-3500 thermal simulator,a mathematical model of the α-phase start transformation temperature for high-Nb pipeline steel was established,based on the transformation kinetics and thermodynamics.The influence of deformation and cooling rate as well as Nb content on the α-phase starting temperature was thoroughly investigated.The results given by the model were in good agreement with the experimental results,which showed that the model could predict the α-phase starting temperature for high-Nb pipeline steel during cooling process. According to the research on the deformation resistance and the ferrite transformation behavior of X80 pipeline steel by using Gleeble-3500 thermal simulator, a mathematical model of the alpha-phase start transformation temperature for high-Nb pipeline steel was established, based on the transformation kinetics and thermodynamics. The influence of deformation and cooling rate as well as Nb content on the α-phase starting temperature was thoroughly investigated. The results given by the model were in good agreement with the experimental results, which showed that the model could predict the α -phase starting temperature for high-Nb pipeline steel during cooling process.