The influence of deformation temperature and strain rate on microstructure of Co4NiCrMo Alloy has been analyzed by isothermal compression test and metallurgical analysis.The results show that the grain size increases with the increase of deformation temperature and the grain size decreases with the increase from 0.001s^-1 to 1s^-1 of strain rate,but increases slightly with the increase from 1s^-1 to 10s^-1 of strain rate.The recrystallization volume fraction increases with the increases of strain and the grain size decreases with the increase of strain.