The behavior of flow stress of Al sheets used for pressure can prepared by different melt-treat- ment during plastic deformation at elevated temperature was studied by isothermal compression test using Gleeble1500 dynamic hot-simulation testing machine. The results show that the Al sheets possess the remarkable characteristic of steady state flow stress when they are deformed in the temperature range of 350-500°C at strain rates within the range of 0.01-10.0s-1. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate, and an Arrhenius relationship with the temperature, which implies that the process of plastic deformation at ele- vated temperature for this material is thermally activated. Compared with the Al pieces prepared by no or conventional melt-treatment, hot deformation activation energy of Al sheets prepared by high-efficient melt-treatment is the smallest (Q = 168.0kJ/mol), which reveals that the hot work- ing formability of this material is very better, and has directly to do with the effective improve- ment of its metallurgical quality. The behavior of flow stress of Al sheets used for pressure can prepared by different melt-treat-ment during plastic deformation at elevated temperature was studied by isothermal compression test using Gleeble 1500 dynamic hot-simulation testing machine. The results show that the Al sheets possess the remarkable characteristic of steady state flow stress when they are deformed in the temperature range of 350-500 ° C at strain rates within the range of 0.01-10.0s-1. A hyperbolic sine relationship is found to correlate well the flow stress with the strain rate, and an Arrhenius relationship with the temperature, which implies that the process of plastic deformation at ele- vated temperature for this material is thermally activated. Compared with the Al pieces prepared by no or conventional melt-treatment, hot deformation activation energy of Al sheets prepared by high-efficient melt-treatment is the smallest (Q = 168.0 kJ / mol), which reveals that the hot work-ing formability of this materi al is very better, and has directly to do with the effective improve- ment of its metallurgical quality.