Conventional lithium-ion batteries using organic liquid electrolytes suffer from limited energy density and safety risks. To improve energy density and safety, all-solid-state lithium battery are developed using solid electrolytes. Among various inorganic solid-state electrolytes, the garnet-type Li7La3Zr2O12 electrolytes have attracted a great deal of attention, owing to high ionic conductivity and the excellent stability against Li metal. In order to further improve the conductivity, the garnet-type electrolytes Ta and Ba co-doped Li7La3Zr2O12 (Li7-x+yLa3-yBayZr2-xTaxO12) were prepared using solid-state synthesis method. The crystal structure, morphology and ionic conductivity of Li7-x+yLa3-yBayZr2-xTaxO12 (0.4≤x≤0.6, 0≤y≤0.05) electrolytes were systematically investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and electrochemical impedance spectroscopy (EIS), respectively. The results show that Ta5+ doping stabilizes the cubic phase. Meanwhile, Ba2+ as dopand and sintering agent can decrease the total resistance by promoting the growth of grains and ceramic densification. Notably, the Li6.45La2.95Ba0.05Zr1.4Ta0.6O12 sample presents a total conductivity of 1.07×10-3 S·cm-1 at room temperature and an activation energy of 0.378 eV. Ta5+/Ba2+ co-doping strategy is conducive to the preparation of garnet-type electrolyte materials with high density and high conductivity.