High　temperature　isothermal　compression　test　of　3003　aluminum　alloy　at　deformation　temperature　of　300-500　℃　and　strain　rate　of　00l-100　s-1　was　carried　out　on　a　Gleeble-1500　thermal　simulator.　The　peak　flow　stress　constitutive　model　of　the　alloy　was　established　by　Zener-Hollomon　parameter　model.　According　to　the　observation　of　microstructure,　the　softening　mechanism　of　hot　deformation　of　the　3003　aluminum　alloy　is　mainly　dynamic　recrystallization(DRX).　With　the　decreasing　of　lnZ　value,　the　dynamic　recrystallization　is　more　fully.　When　lnZ　is　high,　the　softening　mechanism　of　the　3003　aluminum　alloy　during　hot　deformation　is　mainly　dynamic　recovery,　and　the　critical　condition　of　dynamic　recrystallization　of　the　alloy　is　T≥　400　℃,　lnZ≤3198.　The　critical　strain　of　dynamic　recrystallization　of　the　alloy　calculated　by　the　strain　hardening　rate　is　ε＞εc=000532lnZ-012452,　its　value　is　proportional　to　the　Z　parameter.　©　2017,　Editorial　Office　of　Transactions　of　Materials　and　Heat　Treatment.　All　right　reserved.