Carbon/carbon nanotubes (C/CNTs) hybrid membranes are successfully fabricated by pyrolyzing poly (amic acid) (PAA) precursors incorporated with CNTs. The morphology and gas separation performance of the hybrid carbon membranes are analyzed by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM) and single gas permeation test (H-2, CO2, O-2, N-2, and CH4). The effects of CNTs properties (CNTs type, concentration, length and diameter) of on gas separation performance of the hybrid carbon membranes are systemically investigated. The results show the combination of carbon molecular sieve membranes (CMSMs) with CNTs exerts a significantly favourable effect on the enhancement of gas separation performance. Carbon membrane incorporated by multi-walled carbon nanotubes (MWCNTs) shows higher permeabilities but lower selectivities than that embedded by single walled carbon nanotubes (SWCNTs). After acid treatment, the improvement on gas permeabilities by MWCNTs tunnels is not significant when facing the compaction of membrane structure. With the increase of MWCNTs concentrations, the hybrid carbon membrane exhibits significant enhancement in gas permeabilities. In addition, MWCNTs with long length and large diameter usually produce high gas permeabilities. (C) 2017 Elsevier B.V. All rights reserved.