The hot compression behavior of AISI 321 austenitic stainless steel was studied at the temperatures of 950- 1100 C and the strain rates of 0.01-1s1 using a Baehr DIL-805 deformation dilatometer. The hot deformation equations and the relationship between hot deformation parameters were obtained. It is found that strain rate and deformation temperature significantly influence the flow stress behavior of the steel. The work hardening rate and the peak value of flow stress increase with the decrease of deformation temperature and the increase of strain rate. In addition, the activation energy of deformation (Q) is calculated as 433.343kJ/mol. The microstructural evolution during deformation indicates that, at the temperature of 950C and the strain rate of 0.01s1 , small circle-like precipitates form along grain boundaries; but at the temperatures above 950C, the dissolution of such precipitates occurs. Energy-dispersive X-ray analyses indicate that the precipitates are complex carbides of Cr, Fe, Mn, Ni, and Ti. The hot compression behavior of AISI 321 austenitic stainless steel was studied at the temperatures of 950- 1100 C and the strain rates of 0.01-1s1 using a Baehr DIL-805 deformation dilatometer. The hot deformation equations and the relationship between hot deformation parameters were It is found that strain rate and deformation temperature significantly dominant the flow stress behavior of the steel. The work hardening rate and the peak value of flow stress increase with the decrease of deformation temperature and the increase of strain rate. The microstructural evolution during deformation that that at the temperature of 950C and the strain rate of 0.01s1, small circle-like precipitates form grain boundaries; but at the temperatures above 950C, the dissolution of such precipitates occurs. Energy-dispersive X-ray analyzes that that the precipitates are complex carbides of Cr, Fe, Mn, Ni, and Ti.