Abstract: Hot compression test for 7150 aluminum alloy were preformed on Gleeble-1500 at the temperature of 450 ℃ and the strain rate of 10 s-1 with different true strains of 0.2, 0.4, 0.6, 0.8. The microstructural evolution was studied by optical microscopy and transmission electron microscopy. The results show that the true stress increased rapidly with the increase of the true strain and up to a peak value, then followed by a gradual decrease, which showed a dynamic flow softening. The equiaxed grains were elongated and the microstructure evolved from dislocation tangles to dislocation cell and sub-grain with the increase of the true strain. The T (AlZnMgCu) phase and the Al3Zr precipitated phase coarsened and thus weakened the influence of them on inhibiting dynamic recrystallization.