A study was conducted on 7055 Al alloys processed by Equal-channel Angular Pressing (ECAP). The quantitative information about precipitate size, distribution and volume fraction in ECAPed samples was investigated by small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). It is found that with the number of ECAP increasing, the quantitative information about volume fraction (fv), precipitate size (R), specific inner surface of particle-matrix (Sp), and integrated intensity (Q0) all increased, indicating that ECAP enhanced the nucleation and growth of precipitates. The microhardness of samples after two passes of ECAP is higher than that of T6 treated samples even after 96 h at 120°C. The formation of fine grains, higher volume fraction of precipitates, together with strain hardening induced by severe deformation are the main factors leading to a high microhardness in ECAPed samples.