Abstract: The hot deformation behavior of 0Cr16Ni5Mo martensitic stainless steel with different nitrogen contents was studied on a Gleeble3800 thermal machine. The true strain-stress curves and deformed microstructures of the tested steels were investigated. The result shows that with an increase in nitrogen content, the stress increases and the recrystallized grain size reduces. Using the flow stress equation combined with Zener-Hollomon parameters, three constitutive equation models were established. Comparing the stress values from the constitutive equation models and the experiment, the hyperbolic sine model performed best. So, the constitutive equations for the tested steels were obtained by using the hyperbolic sine mode, with some improvements made during the calculation.