In order to optimize the hot working technology of Incoloy 800H,the dynamic recrystallization(DRX) behavior of Incoloy 800H at temperatures ranging from 850°C to 1100°C and strain rates from 0.01 s~(-1) to 10 s~(-1) was investigated by single-pass compression tests on MMS- 300 thermo-mechanical simulator.The evolutions of microstructure and nucleation mechanisms of DRX were analyzed combined with the technique of EBSD and TEM.The results show that when the deformation temperature is below 950°C,the behavior of DRX is obviously restrained by precipitation of Cr_(23)C_6 and Ti(C,N).Therefore the hot deformation constitutive equations in two temperature intervals(from 850°C to 950°C and from 950℃to 1100°C) were established by regression analysis with the deformation activation energy of 465.394 kJ/mol and 427.360 kJ/mol respectively.The inflection points were determined by fitting a third order polynomial to the lnθ-ecurves,which makes the prediction for the ratios of critical stress to peak stress and critical strain to peak strain more accurately. Accordingly,the mathematical models of critical stress and critical strain vs Z parameter were deduced.The DRX nucleation mechanisms of Incoloy 800H during hot deformation mainly include strain induced grain boundary migration,grain fragmentation and subgrain coalescence.