Abstract: In the present work, the flow stress of FeCrNi alloy is dividedinto two parts, athermal stress (long-range) and thermally activated stress(short-range), based on the dislocation dynamics of plastic deformation ofmetal material. Firstly, the yield stress, twins and dislocationconfigurations of the alloy are analyzed with the effect of temperature andstrain rate. Hence, modified Johnson-Cook model is introduced to describethe athermal stress. Secondly, the distance between dislocation barriers\Delta l was found to mainly affect the thermally activated stress andthe g(\gamma, \dot \gamma, T) function was educed andinput in the Kocks model. Therefore theconstitutive model of FeCrNi alloy was developed to describe the plasticresponse of FeCrNi alloy from low temperature to high temperature, andfrom static loading to dynamic loading.