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The electrical conductivities of Sr 2 CoRO 6 (R=Mo, Nb) under different oxygen partial pressures and their crystal structures were investigated. Their conducting mechanisms were proposed. X-ray photoelectron spectra revealed that the dominated oxidation state of Co 2+ was in Sr 2 CoMoO 6 but Co 3+ in Sr 2 CoNbO 6 . The crystal lattice structures of Sr 2 CoRO 6 were identified by X-ray diffraction and their parameters were calculated by using Rietveld method. The refined crystal structures of Sr 2 CoRO 6 have been used to construct their own conducting channel model. And the electrical conductivities were measured by using an electrochemical workstation with four-terminals method through controlling the oxygen partial pressure of the testing environment. The results show that the electrical conductivity of Sr 2 CoMoO 6 is 0.36 S·cm ¹1, much lower than that of Sr 2 CoNbO 6 (7.81 S·cm ¹1) in air at 973 K, which is assigned to the difference of their conducting channels. And the electrical conductivity of Sr 2 CoMoO 6 increased linearly with the decrease in P O2 , reaching 2.05 S·cm ¹1 when P O2 = 10 ¹21 atm at 973 K, while Sr 2 CoNbO 6 presented an opposite trend. It was supposed that the different valences of cobalt in Sr 2 CoMoO 6 and Sr 2 CoNbO 6 lead to the different electron conducting channels and different changing trends of electrical conductivities with the decrease in oxygen partial pressure.