Abstract: Rare earth composite oxides La0.7Sr0.2Ca0.1Co1-xFexO3-δ(x=0.3,0.5) doped with Sr,Ca and Fe were synthesized by solid state reaction.The forming process of the products was analyzed by TG-DTA testing.The mixed conductivity and thermal expansion coefficient(TEC) of the products were measured in 100-900 ℃.The crystal structure and grain morphology of the products were characterized.The results show that both the two oxides had a single rhombohedral perovskite structure,and the grain growth was good,but the size was not uniform enough after sintering at 1 200 ℃.The mixed electrical conductivity increased first and then decreased with the increase of temperature.The conductivity of the two oxides was larger than 100 S·cm-1 at 600-800 ℃ which could meet the demand.The conductivity kept linear relation with the temperature which showed that the conductive behavior accorded with the small-polaron conductive mechanism at 100-500 ℃.Ca and Fe doping at the same time could effectively reduce the TEC which indicated that the thermal-stability of the perovskite lattice increased.