An oxygen permeation model for an asymmetric membrane made by phase-inversion is developed to link the permeation performance directly to measurable variables, such as experimental conditions and geometric parameters. Zr0.84Y0.16O1.92-La0.8Sr0.2Cr0.5Fe0.5O3-delta (YSZ-LSCrF) membrane is selected as representative membrane. The percolation theory is used to describe the effective properties of the composites. Two permeation modes in asymmetric membrane are compared. One mode is oxygen permeation from the Support to the thin Dense layer (SD mode), and the other oxygen permeation flux is the opposite way (DS mode, from dense layer to support). In these two modes, the maximum oxygen permeation rate is achieved at an ionic phase fraction of 0.5 under air/CO gradient. It is also found that it is beneficial for the membrane to obtain higher oxygen permeation flux when DS mode is adopted for the supported membrane. In addition, the surface exchange on lean side in SD mode limits the whole oxygen permeation. The resistances of support layer and dense layer in asymmetric membrane are calculated. The rate-limited step is identified by distribution of these resistances. (C) 2015 Elsevier B.V. All rights reserved.