The dense ceramic oxygen-permeable membrane has attracted much attention due to its potential applications in production of oxygen from air and manipulation of oxygen-consuming industrial chemical processes. In the present study, Gd_0.1Ce_0.9O_2-δ-La_0.6Sr_0.4FeO_3-δ (GDC-LSF) dual-phase composite membrane was prepared using the phase-inversion tape casting/lamination/sintering method. The as-prepared membrane consisted of an 80 μm thick dense oxygen separation layer sandwiched between two 420 μm thick finger-like porous support layers. The inner surface of the support layers was further modified with Nd₂NiO_4+δ (NNO) nanoparticles using the impregnation method. An oxygen permeation flux of 1.53 mL·cm^-2·min^-1 was measured at 900 ℃ by exposing one side of the membrane to a flowing air stream and the other side to a flowing He stream. When CO₂ was used as sweep gas, an oxygen permeation flux of 0.6 mL·cm^-2·min^-1 was obtained, and no decrease in the flux was observed during 90 h of testing. The membrane remained intact after experiencing over 70 thermal cycles between 800 and 900 ℃. GDC-LSF dual-phase composite membrane with straight pores and sandwich structure has demonstrated satisfactory combination of oxygen permeability, chemical stability and thermal mechanical strength, promising for applications in separation of oxygen from air and oxy-fuel combustion with CO₂ capture.