A novel molecular sieve membrane was synthesized using graphene oxide/single-walled carbon nanotubes (GO/SWCNTs). The composite was characterized by transmission electron microscopy, field emission scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller-specific surface area analyzers. The results revealed that laminar GO was interwoven with tubular SWCNTs and the carbon nanotubes were attached onto the surface of GO or interspersed among GO to form a three-dimensional structure. Moreover, the interlayer spacing of GO/SWCNTs increased to 0.826 nm. On condition that the inlet pressure of N2 was 0.10 MPa and the temperature was 323 K, the N2 permeability of GO/SWCNTs was 1595 Barrer. With increasing temperature, the N2 permeability decreased while it increased with the inlet pressure. When the inlet pressure of CO was 0.10 MPa and the temperature was 323 K, the CO permeability was 109 Barrer. At the temperature of 323 K, the selectivities of N2/CO and CO2/CO were 32.8 and 37, respectively. These results indicated that GO/SWCNTs may be a promising molecular sieve for gas separation. © 2020 Lili Jiang et al.