This paper mainly studied the change rule of aging treatment temperature and aging holding time on the structure and performance of 7075 aluminum alloy laser weld. Scanning Electron Microscopy (SEM) was used to observe the chain T phase formed during welding. With the extension of heat preservation time, the T phase melted into the substrate gradually. After aging treatment temperature 120 ℃ at 24 h,the T phasewas uniformly distributed in a spherical shape, which reduced its cleavage effect on the matrix. TEM and SADE image showed that the nanoscaleη" phase was precipitated on the crystal axis of [011]Al、[12]Al、[001]Al. With the extension of time, the size and distribution density of η" changed and gradually becameη. The phase prevented dislocation movement to improve the mechanical properties of welds. By comparing the microhardness and tensile strength, 7075 aluminum alloy laser welded joint has the best mechanical properties by aging treatment temperature 120 ℃ at 24 h.