Abstract: On the basis of summarizing and evaluating the phase diagram, thermodynamic data and crystal structure data of Al₂O₃-V₂O₅ system, thermodynamic optimization of Al₂O₃-V₂O₅ system is carried out by using phase diagram calculation method. The liquid phase is described by the modified quasichemical model with the pair approximation, which takes short-range ordering in liquid solution into account. The VO₄^3- is considered as the basic building unit of V₂O₅ in the liquid solution and the maximum short-range ordering is set at the AlVO₄ composition. The AlVO₄ phase is treated as stoichiometric compound. The experimental data are reproduced well and a set of self-consistent model parameters is obtained to describe the thermodynamic property of every phase in this binary system. The present study can be used as a basis for improving the catalytic performance of the catalyst supporting V₂O₅ on Al₂O₃.