Abstract:The subjects of this paper is ultra-high strength aluminum alloy Al-10.78Zn-2.78Mg-2.59Cu-0.22Zr-0.047Sr, which was involved in the process of solution - aging and thermomechanical treatment(solution-overaging-hot compression) - solution - aging. Electron back scattering diffractions (EBSD) technology, X-ray diffraction (XRD) and tensile testing were respectively used on its study of distribution of grain and grain boundaries, internal dislocation density and tensile properties, and dislocation strengthening and grain boundary strengthening are calculated quantitatively. The results show that TMT refines grain with average grain size reducing from 7.30 μm to 6.04 μm and misorientation angle reducing from 21.45 to 21.04 . TMT increases peak aging hardness from 214.6 HV(120℃×48h) to 226.8 HV(100℃×48h), but has little effect on strength with yield strength are both almost 600 MPa. The tensile fracture morphology of alloys both?display intergranular and tear fracture. Dislocation density of alloys processed by solution and TMT - solution are both 0, and TMT reduces sum of dislocation strengthening and grain boundary strengthening from 58.8 MPa to 57.4 MPa.