Basic aluminum sulfate (BAS) wet flue gas desulfurization (FGD) is a promising renewable process used to remove sulfur dioxide (SO2) from flue gas, in which the regeneration of BAS SO2-loaded solution is of great importance for the reuse of BAS solution. In this paper, a novel regeneration method by vacuum desorption was developed to achieve superior regeneration performance for a BAS-rich solution. The operating parameter effect on SO2 desorption performance was thoroughly investigated in a lab-scale reactor. The experimental results demonstrated that the great decrease of pressure could significantly improve the regeneration performance, and high desorption temperature was favorable for SO2 desorption. Furthermore, it is worth determining the optimum components of a BAS-rich solution and initial sulfite concentration, considering the contradiction between the SO2 absorption performance and the regeneration performance. The increase of stirring speed in the liquid had a considerable positive effect on SO2 desorption efficiency. In addition, through a simple comparison with direct heating regeneration, it indicates that the utilization of vacuum regeneration could have the potential to improve the regeneration rate and lower the total energy consumption. Finally, the recycling experiments of the absorption desorption process show that the BAS solution could be reused successfully to capture SO2 from flue gas by vacuum regeneration, while SO2 absorption efficiency would decrease to below 90% after 11 cycles, attributed to the inevitable oxidation of byproduct in the desulfurization process.