As a mixed conductor,LaSr3Fe3O10-δ with triple layer perovskite intergrowth structure can be used as an oxygen separation membrane material and cathode material in solid oxide fuell cells.LaSr3Fe3O10-δ was synthesized via citrate acid route.Iodine titration method was used to determine the average valence of transition metal Fe and oxygen nonstoichiometry δ.Conductivities of LaSr3Fe3O10-δ were measured in the oxygen partial pressure range from 10-2×105 to 1×105 Pa,by Ac four probe method.Seebeck coefficient measurement together with conductivity results indicated that LaSr3Fe3O10-δ is a p-type conductor.A linear relationship between the conductivity and logarithm of oxygen partial pressure was observed in the measurement,A defect model was introduced to explain the observed phenomena in the iodine titration,conductivity and Seebeck coefficient measurement.Electrical conductivity relaxation method was used to determine the oxygen chemical diffusion coefficient Dchem.The apparent activation energy of oxygen chemical diffusion was calculated to be 61.4 kJ/mol.