aluminum alloy with different states (T6 and solution treatment) were forged at different strain rates (10-2s-1 and 102s-1) and strains. OM (optical microscope) and TEM (transmission electronic microscope) were used to observe the microstructure of 7075 aluminum alloy after hot deformation. Experiment results indicate that dynamic recrystallization for 7075 aluminum alloy is apt to occur under the higher strain rate and recrystallization mechanism is discontinuous dynamic recrystallization, dynamic recovery takes place at the lower strain rate. The second-phase particles play a very important role in the process of refinement of the grains.