The mechanical properties of the 7xxx series aluminum alloy deposited specimens are low due to the uneven microstructure and element segregation in the process of wire and arc additive manufacturing (WAAM). In order to solve this problem, the 7075 aluminum alloy thin-walled specimens deposited by WAAM were subjected to solid solution + artificial aging heat treatment (T6 state). The microstructure evolution and mechanical properties before and after heat treatment were investigated. The results showed that the grains in the as-deposited specimen were surrounded by eutectics with network-like structure, and the elements of Zn, Mg and Cu were concentrated at the grain boundaries, resulting in the element segregation. After T6 heat treatment, most of the eutectics were dissolved. Moreover, the unevenness of the element distribution was significantly reduced. Compared with the as-deposited specimens, the tensile strength and elongation of T6 specimens were improved. The value of tensile strength increased from (279.4±5.3)MPa to (493.9±10.2)MPa, and the elongation increased from 3.78 %± 0.35% to 9.66% ± 1.70%. The tensile fracture surface of T6 specimen was densely covered with dimples. Therefore, the fracture mode was ductile fracture.