Molecular oxygen diffusion in the cellulose acetate membranes containing the 5,10,15, 20-tetrakis(pentafluorophenyl)-21H,23H-porphine iron(II) was studied. Both the permeability coefficient and the separation factor for oxygen in the membrane containing the iron(II) porphyrin complex were increased with decreasing the upstream gas pressure which correspond to a dual-mode oxygen transport. The effects of the axial ligands of the iron(II) porphyrin on oxygen permeation was also examined in the same cellulose acetate membrane. The fluoride and 2-methyl imidazole ligands coordination to the iron(II) porphyrin induce to increase the oxygen permeability coefficient and the value of ideal separation factor.