The co-doped solid electrolyte Ta1-x-yTixSnyO2.5-δ(x=0.077,y=0-0.053) material with triclinic structure was prepared by oxalate coprecipitation method. The thermal and electrical properties of the solid electrolyte were analyzed by X-ray diffraction analysis(XRD), Scanning electron microscope(SEM), Differential thermal analysis(DTA), Electrochemical impedance spectroscopy analysis(EIS). The study found that after co-doping with Sn4+/ Ti4+, the high temperature triclinic phase of tantalum oxide-based electrolyte was stabilized to room temperature, and more oxygen vacancies were generated due to doping in its structure, thus improving the conductivity of tantalum oxide-based electrolyte. At working temperature of 973 K, the solid electrolyte Ta0.89Ti0.077Sn0.033O2.5-δ has an ion conductivity of 0.76×10-1 S/cm and activation energy of 0.696 eV. The co-doped solid electrolyte has a low thermal expansion coefficient of 3.78×10-6 K-1, which is a low-expansion material, and the solid electrolyte has good thermal stability.