The　behavior　of　flow　stress　of　Al　sheets　used　for　pressure　can　prepared　by　different　melt-treatment　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°C-500°C　at　strain　rates　within　the　range　of　0.01-10.0　s-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　elevated　temperature　for　this　material　is　thermally　activated.　Compared　with　the　Al　pieces　prepared　without　such　melt-treatment　or　by　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　working　formability　of　this　material　is　far　better,　and　has　directly　to　do　with　the　effective　improvement　of　its　metallurgical　quality.