This work investigated the influence of Li₂O as a sintering aid on the sintering behavior of La_0.8Sr_0.2Ga_0.8Mg_0.2O_3-δ (LSGM) electrolytes in solid oxide fuel cells, which systematically presented the effects of sintering aid content and sintering temperature on the density, microstructure, phase composition, and the ionic conductivity of sintered LSGM bulk. The results show that addition of Li₂O sintering aid not only reduces the sintering temperature, but also eliminates the LaSrGa₃O₇ impurity phase in the sintered LSGM and suppresses the formation of MgO impurity phase which is easily generated during the conventional sintering process. Moreover, the addition of Li₂O increases the ionic conductivity of sintered LSGM electrolytes. When 1% (molar percentage) Li₂O is added, the LSGM bulk sintered at 1400 ℃ for 4 h reaches 99% of the theoretical density and presents a single perovskite stracture. When tested at 800 ℃, the ionic conductivity of the sintered bulk reaches 0.17 S/cm, which is 20% higher than that of the sample without sintering aid. All results demonstrate that adding an appropriate amount of Li₂O as sintering aid is of great significance for the application of high ionic conductivity electrolyte in intermediate- temperature solid oxide fuel cells (IT-SOFCs).