The quasi-thermodynamics and the kinetics of deformation-induced non-equilibrium grain boundary segregation are described. This model is used to predict non-equilibrium segregation of P during high temperature plastic deformation in an austenite microstructure. There is a segregation concentration peak of P near 800 ℃ for a strain rate of 1×10-3 s-1 and the deformation magnitude is 20%. When the deformation reaches 20% in magnitude at 1000 ℃ the segregation of P at grain boundaries increases with increasing strain rate. The predictions are generally consistent with some available experimental observations.