The lattice constant, vibration entropy, thermodynamic transition energy level and intrinsic point defect formation energy in Y₂O₃ crystal were studied by computer simulations with VASP and GULP softwares. Considering the contribution of lattice vibration entropy, the formation energy of defects in the form of vacancies, interstitial and antisite with the changes in temperature and oxygen partial pressure was investigated. The results show that with the increase of temperature and oxygen partial pressure, the most stable defects near the top of the valence band is ${\rm{Y}}_{\rm{i}}^{ {\text{·\!\!\!·\!\!\!·}}}$, and the most stable defect near the bottom of the conduction band changes from ${\rm{V}}_{\rm{Y}}^{'''}$ to ${\rm{O}}_{\rm{i}}^{''}$. The calculations also prove that the type and concentration of oxygen vacancies can be adjusted by varying the temperature and controlling the oxygen partial pressure. In addition, the point defects distribution varying with environmental conditions was clearly presented by using two and three dimensional diagrams, which provides the theoretical basis for crystal growth and annealing environment selection.