Na₁₁Sn₂PS₁₂ solid electrolytes were synthesized by a high-temperature quenching method, and the structures as well as electrochemical performance were investigated. A Na₁₁Sn₂PS₁₂ phase with a certain amount of impurity can be obtained in quenching process. The content of impurity phase in the quenching precursors annealed at 430 ℃decreases and the room-temperature ionic conductivity enhances from 0.34×10^–4 S/cm to 6.26×10^–4 S/cm. In addition, a prepared Na₁₁Sn₂PS₁₂ possesses a low activation energy of 0.27 eV and an electronic conductivity of 2.25×10^–8 S/cm, and an electrochemistry stability window between 0.8 V and 2.8 V. Also, Na₁₁Sn₂PS₁₂ is used in all-solid-state sodium batteries, showing good electrochemical performances.