We report first principles calculations aimed at understanding the dopant chemical potential modulation on the oxygen vacancy formation in In2O3. Relaying on our results, it implies that oxygen vacancies are deep donors in undoped In2O3 and change to shallow donors with embedded Zn and Al in contrast to previous expectations of native carrier from oxygen vacancy. Our results well explain the anomalous carrier concentration increase in Zn and Al codoped In2O3. Our proposed models reveal the chemical potential modulation on oxygen vacancy formation and lead to a natural oxygen vacancy formation mechanism in the presence of metallic dopants in In2O3.