Double perovskite oxide Sr1.85MgMoO6-δ was synthesized by sol⁃gel method in 5% H2/Ar, and its structural stability was characterized by XRD. The experimental results show that the structure and phase composition of Sr1.85MgMoO6-δ have not changed after high temperature oxidation treatment, which fully proves its structural stability. The conductivity, thermogravimetric and electrochemical impedance spectra of Sr1.85MgMoO6-δ and Sr2MgMoO6-δ were measured in the same environment. The experimental results show that Sr vacancy can effectively enhance the conductivity of the material itself and increase the oxygen vacancy of the material. In addition, the polarization impedance value Sr1.85MgMoO6-δ (2.26~0.56 Ω·cm2) in H2 is smaller than that in Sr2MgMoO6-δ (4.80~1.96 Ω·cm2) at 700~800 oC temperature. Therefore, Sr1.85MgMoO6-δ double perovskite material is a very promising medium temperature solid oxide fuel cell (SOFC) anode material.