Abstract: The tensile stress-strain curves of 10CrNi8MoV steel are obtained by controlling the temperature and the strain rate. The flow stress is decomposed into thermal activation stress and non-thermal activation stress according to dislocation dynamics, and the influence of viscous resistance is ignored. Based on the analysis of plastic deformation process, a dislocation spacing evolution function is introduced into Kocks thermal activation equation, and the change of non-thermal activation stress is described by linear strengthening model, so the physical constitutive model of 10CrNi8MoV steel is established. The model can well describe the plastic deformation behavior of 10CrNi8MoV steel in the condition of low strain rate and wide temperature range.