The paper presents a model of oxygen transport in oxygen-permeable hollow fiber membranes taking into account the gradual changes of oxygen partial pressure in flows of feed and sweep gases along the HF membrane. The model is based on fulfilling local mass balance conditions linking oxygen flows in feed and sweep gases with the oxygen flux through the membrane. Computer simulation of oxygen permeation data for hollow fiber membranes made from mixed ionic electronic conducting oxides (Ba 0.5 Sr 0.5 Co 0.8 Fe 0.2 O 3- δ , Ba 0.5 Sr 0.5 Co 0.78 W 0.02 Fe 0.2 O 3- δ and Ba 0.5 Sr 0.5 Co 0.75 Mo 0.05 Fe 0.2 O 3- δ ) was carried out using different models. The oxygen permeability model based on the semi-empirical dependence of the oxygen flux on oxygen partial pressure J O 2 =γ(T)(pO 2,1 n -pO 2,2 n ) gives the most accurate description of the experimental data. An analysis of the activation energy of the effective oxygen flux coefficient γ(T) indicates that the rate determining step is a surface reaction.