Abstract: In order to study the effect of equal channel angular pressing (ECAP) on the microstructure and properties of ultra cold ultra high strength 7055 aluminum alloy, the aluminum alloy was heated to 480 ℃ for ECAP hot extrusion test, and then its microstructure and properties were detected and analyzed by OM, EBSD, TEM and other technical means.The results show that the average grain size of 7055 aluminum alloy is significantly reduced, and the proportion of large angle grain boundary is reduced, but it is still higher than or equal to 66%, the proportion is still high. Moreover, a large number of dislocations are introduced into the matrix by ECAP, which promotes the nucleation of precipitates, enhances the precipitation strengthening effect of the alloy; at the same time, the hardness of the alloy also has a certain improvement.By applying large shear deformation to a certain volume of material, the ECAP process can effectively refine the grain size, improve the microstructure of the material, and improve the comprehensive mechanical properties of the material, such as strength and toughness.