This paper describes the study on H-2/CO mixture gas separation through thin film composite (TFC) membranes prepared by interfacial polymerization method. Composite membranes have been widely applied in gas separation process. Polyethersulfone (PES) hollow fiber membranes (HFMs) are fabricated using dry-wet phase inversion method as high permeability substrates. H-2/CO mixture gas selectivity and permeance were studied using different concentrations of aqueous and organic phase monomers. Cross-linked structures of TFC membranes by interfacial polymerization were confirmed and discussed by using the compiled results of characterization, such as ATR-FTIR, FE-SEM, and TEM. The performance of HFM using different monomer concentrations of 1,3-cyclohexanebis methylamine (CHMA) (aqueous phase monomer) and trimesoyl chloride (TMC) (organic phase monomer) towards H-2/CO mixture gas selectivity and permeance have been studied, and the effects of operating pressures, retentate flow rates and stage-cuts on separation factor and permeance were also investigated in this work. The monomers concentrations affect the selectivity and permeability in H-2/CO mixture gas separation. Experimental results confirmed that increasing of operating pressure and stage-cut led to higher separation factor and showed simulation of module design to consider characteristics of membrane and behaviors for H-2/CO mixture gas separation. In this paper, also represent the membrane spinning, polymerization and Membrane process design. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.