Abstract. Biopolymer are expected to be environmentally compatible and to have great potential application as membranes material. The chitosan-poly (ethylene glycol)/PEG based composite membranes was successfully synthesized via inversed phase method. The effect of multiwalled carbon nanotubes (MWCNT) as nanofiller on properties and performances of composite membranes were intensively evaluated. The membrane was prepared by mixing of chitosan and PEG solutions at the same composition ratio while MWCNT amount in the mixture was varied. The synthesized membrane was characterized by means of FTIR spectroscopy, scanning electron microscopy (SEM), contact angle, and tensile strength measurement. The performance of composite membrane on filtration was evaluated in term of flux (permeability) and rejection (rejection) tests. The results showed that the optimum volume ratio of composite membrane solution was found at 30:10:7.5 for chitosan/ PEG/ MWCNT, respectively, as indicated by the largest flux. Insertion of MWCNT nanofiller notably enhanced hydrophilicity, porosity, and mechanical properties of composites membranes that are confirmed by contact angle, SEM images and elongation forces value, respectively. The MWCNT nanofiller remarkably increased both of flux and rejection of composite membranes up to 60 Lm 2 h -1 and 96%, respectively. The remarkable enhancement of composite membrane performance is attributed to the effective interaction of MWCNT with polymeric matrix.