Abstract: The metal-plastic deformation resistance of ML40Cr steel had been studied by isothermal compression test in the Gleeble-3800.The results show that ML40Cr steels after plastic deformation have strengthen.The deformation resistance increase with increasing deformation degree.Dynamic recrystallization occur at low strain rate and more than 1 000 ℃.The deformation resistance increase with increasing strain rate.Most of condition,the flow stress decrease with the increase of deforming temperature,on the contrary in two-phase region and low strain rate.Additionally,the deformation resistance expression is regressed using origin soft.It could offer theoretic base to calculate rolling force of ML40Cr steel.