Abstract: The flow stress behavior of a new type Al-Cu-Li system alloy during hot compression deformation was studied in the strain rate range from 0.01 to 10 s^-1 and the temperature range from 300 to 500℃ by isothermal compression test on a Gleeble 1500 thermal-mechanical simulator. The results show that the flow stress of this new type Al-Cu-Li system alloy decreases with the increase of deformation temperature and increases with the increase of strain rate. The peak flow stress during high temperature deformation can be represented by Z parameter in a hyperbolic sine function. The analytical expression of peak flow stress was fitted with the hot deformation activation energy of 239.02 kJ·mol^-1.