During the processing of hot working, the material undergoes shape and microstructural changes depending on the processing history. Therefore, the optimization of the processing parameters such as temperature, strain and strain rate is of great importance to achieve a defect-free component with desired microstructure. In order to optimize the hot working technology, the hot deformation behavior and hot workability of alloy 800H in the temperature range of 850-1100℃ and strain rate range of 0.01-30 s^-1 were investigated with single-pass compression tests on MMS-300 thermo-simulation machine. The flow stress-strain curves of alloy 800H under different deformation conditions were plotted. The influence of precipitation on hot deformation below 950℃ at low strain rates was studied. The processing map was established based on dynamic materials model. The effect of processing parameters on hot workability and the mechanism of hot deformation in different regimes of processing map were analyzed combined with the observation of microstructural evolution. The results revealed that the adiabatic heating is generated obviously if strain rate is higher than 1 s^-1 during hot deformation, which leads to flow softening via the mechanism of rotational dynamic recrystallization (DRX). Some ultrafine grains can be found in the core of shear bands. The magnitude of temperature rising and subsequent softening are supposed to be more significant at higher strain rates or lower deformation temperatures. The occurrence of DRX is inhibited by “Zener effect'' which pins the migration of grain boundaries and increases the activation energy of hot deformation. The alloy 800H exhibits a better workability in deformation temperature range from 975℃  to 1100℃ and strain rate range from 0.01 s^-1 to 0.3 s^-1 with the efficiency of power dissipation within the range of 35%—48%.