Abstract: AZ80 magnesium alloy single pass wall part was fabricated by CMT wire arc additive manufacturing（CMT-WAAM）, and the effects of T4 process with different solution time at 490 ℃ and T6 process with different aging time at 170 ℃ on the microstructure and mechanical properties of WAAMed AZ80 magnesium alloy were systematically studied.The results show that the as-deposited AZ80 alloy exhibits uniform grain distribution in the upper, middle and lower regions,the microstructure consists of α-Mg, β-Mg₁₇Al₁₂and Al₈Mn₅, and the difference in the content of the second phase is relatively small. However, its yield strength remains relatively low, which is 118 MPa. T4 treatment effectively eliminates segregation and dissolves the β-Mg₁₇Al₁₂phase, but with the increase of the solution time, the second-phase strengthening effect weakens,leading to a decline in mechanical properties. In contrast, the T6 treatment induces the reprecipitation of β-Mg₁₇Al₁₂and Al₈Mn₅phases and the formation of twin crystals, resulting in age-hardening. After 28 h of aging, the alloy reaches peak hardness, the yield strength increases by 49.15% and57.14% compared with that of the as-deposited and T4-treated states, respectively. The study elucidates the regulatory mechanisms of heat treatment on the microstructure and properties of AZ80 magnesium alloy,which can provide a theoretical basis for optimizing its strength and toughness.