Effects of strain on microstructure behavior of 7050-H112 aluminum alloy was investigated by means of hot compression conducted at 450 A degrees C and strain rate of 1 s(-1). The true stress-true strain behavior shows that it appears dynamic soft after acquired peak stress. The microstructure evolutions are mainly characterized by dislocation substructures with low misorientations which increase with deformation at low to medium strains, but decrease at high strain. It is concluded that the main soft mechanism is dynamic recovery with partial dynamic recrystallization at low to moderate strain, and then dynamic recrystallization at high strain. At last, the substructure behavior which is mainly affected by dislocation migrations is discussed in detail. At low deformation, dislocation migration can destroy grain boundaries and their junctions, resulting in formation of low angle boundaries. However, the interactions of dislocations increase with increasing of deformation, leading to a evolution of high-angle boundaries.