Perovskite-type ceramic powder, La(0.7)Sr(0.3)Co(0.3)Fe(0.7)O(3-δ), have been synthesized successfully by the citrate method. As a result of TGA for precursor, metal-citrate complex in precursor was decomposed in the temperature range of 150~650 ℃. XRD analysis showed the single perovskite structure was observed over 1,000 ℃ without impurities. Typical dense membrane with 1.6 mm thickness has been prepared using as-prepared powder by pressing unilaterally and sintering at 1,300 ℃. The electrical conductivity of La(0.7)Sr(0.3)Co(0.3)Fe(0.7)O(3-δ) membrane increased with increasing temperature at atmosphere of air and then decreased over 600 ℃ due to oxygen loss from the crystal lattice. The oxygen flux of La(0.7)Sr(0.3)Co(0.3)Fe(0.7)O(3-δ) membrane in the range of 700 to 950 ℃ increased with the increasing temperature from 0.045 to 0.415 ml/cm2·min. The activation energy for oxygen permeation was calculated to be 89.17 kJ/mol.