Grain size and microstructure evolution mechanisms for 2A02 aluminum alloy under different deformation and heat treatment conditions have been investigated by means of hot working simulator and OM and TEM analysis. The results show that when the hot deformation was lower than 40%, work hardening dominated the forging processes. When the hot deformation was up to 60%, work hardening and dynamic softening dominated by geometric dynamic recrystallization (GDRX) interacted and went to a balance, inducing the obvious zigzag type or the serrated grain boundary formed by the movement and merging of sub-grains. During the aging process after the solution treatment, the TEM observation indicates that the dislocation density of equal-axial grains after recrystallization was becoming lower with the increasing of the aging time, while according to the optical microscope results, the longer the aging time was, the larger the obtained equal-axial grains could be.