The present invention discloses a new method to fabricate high performance beta-alumina/YSZ electrolyte at much lower temperatures. With the starting material of Boehmite, pure beta-alumina phase can be formed as low as 900oC. The sintering aid of TiO2 can be added into beta-alumina/YSZ composite, which helps for beta-alumina sintering while MnO2 can be added into the composite to help YSZ sintering. With the addition of both TiO2 and MnO2 in Boehmite/YSZ composite, simultaneous conversion and sintering process occur at as low as 1400oC with the formation of pure beta-alumina phase and almost full dense beta-alumina/YSZ electrolyte.