The microscopic phase-field method was employed to study the antisite defect in Al-9.0at%Li alloys with aged time and tempture. At the same aged tempture, the antistie defect Al_Li and Li_Al in Al₃Li phase which is L12 structure gradually reduced as the aged time wore on. Under Al-rich condition, the concentration of Al_Li antisite defect was higher than the the concentration of Li_Al antisite defect. In Al₃Li phase, the antistie defect was mainly about Al_Li, and with a few of Li_Al. Then the aging temperature changed, after Al₃Li phase nucleation stable, with the tempture higher, the concentration of Al_Li and Li_Al antistie defect were higher. Also had the characteristics before the nucleation stable, but the regularity was not remarkable.