Stable solid electrolytes with high lithium ionic conductivity are crucial for all-solid-state lithium ion batteries. The compatibility with electrodes require a sintering temperature around 1000 °C. A perovskite-type (Li,Sr)(Zr,Nb)O3 system with A-site vacancy is designed and synthesized by a solid-state reaction route. Four compositions with different concentrations of A-site vacancy and several sintering temperatures between 1100 and 1300 °C are selected to find an optimal composition. X-ray diffraction and scanning electron microscope are employed to analyze the crystalline phases and the microstructure of the sintered samples. The ionic conductivities of the materials are measured by AC impedance spectroscopy. For the sample with the optimal composition Li3/8Sr7/16Zr1/4Nb3/4O3 and sintered at 1200 °C, its total ionic conductivity is 2.00×10−5 and 1.65×10−4 Scm−1 at 30 and 100 °C, respectively. Its activation energy for lithium ion conduction is 0.26 eV.