Three synthesis methods were compared for the preparation of La-0.2 Sr0.8Co0.2Fe0.8O3-delta (LSCF) powders. It was found that the solid state reaction method is the most easily controlled and effective. A mathematical model in consideration of membrane bulk diffusion and surface reaction has been developed to simulate the performance of the disk-shaped dense membranes for oxygen permeation. The experimental results showed that oxygen permeation flux of the LSCF membrane increases with the decreasing downstream oxygen partial pressure, and the oxygen permeation flux through a 2 mm LSCF membrane is about 0.32 cm(3)/cm(2) min (STP) at 1123 K and the oxygen partial pressure of 0.21/1x10(-3) atm. The characteristic thickness (L-c) of the LSCF membrane was estimated to be 1.8 mm by modeling and experimental study.