10Cr12Ni3Mo2VN steel is mainly made by forging and usually used to make last stage blades of ultra-supercritical unit, demanding strict standards of microstructure property because of its hard service environment, so it is necessary to conduct deep research on its hot deformation behavior. The hot deformation behavior of 10Cr12Ni3Mo2VN steel was investigated through high temperature compression tests on the Gleeble-1500 thermal-mechanical simulator at 850~1200 ℃ and strain rate range of 0.01~10 s^-1. The results show that dynamic recrystallization becomes more prone to happen and recrystallized grain size increases with increasing temperature and decreasing strain rate. Isometric crystal and mixed structure appear after compressed 60% at 1200 ℃ with high and low strain rate respectively. A new method of establishing the hot deformation hyperbolic sine constitutive equation by Levenberg-Marquardt algorithm is proposed. Parameters of the constitutive equations established by traditional linear fitting and Levenberg-Marquardt algorithm have a similar value, and both of the constitutive equations have a high prediction precision, so the method of establishing constitutive equation by Levenberg-Marquardt algorithm is credible. However, Levenberg-Marquardt algorithm can get all parameters at the same time with fewer and simpler steps compared to traditional linear fitting. In addition, the values of critical strain for dynamic recrystallization initiation are determined from the work hardening rate-strain curves and a model related to Zener-Hollomon parameter for predicting critical and peak strain under different deformation paraments is established.