Polyetherimide (PEI) microporous membranes with uniform cellular structure, high porosity, and narrow pore size distribution were formed by supercritical CO2 (ScCO2) phase inversion method, and the membrane was modified to be a matrix for the preparation of affinity membrane due to its low solvent residue and appropriate porous structure. The effects of ScCO2 temperature and pressure on the morphology and pure water flux of the membrane were investigated. The membrane prepared at 24 MPa and 45 degrees C with a large mean cell diameter of 6.0 mu m, high porosity of 73%, narrow pore size distribution and a pure water flux of 56 L/(m(2) h bar) was coated with chitosan to improve its hydrophilicity and coupled with Cibacron Blue F3GA (CB) as a special ligand to form an affinity membrane (PEI-coated chitosan-CB membrane). The PEI-coated chitosan-CB membrane showed a high adsorption capacity of 33.9 mg/g membrane to bovine serum albumin and was higher than most of affinity membranes. Moreover, the tensile strength of PEI-coated chitosan-CB membrane was 11.58 MPa and was much higher than those of affinity membranes. This work demonstrates that ScCO2 phase inversion method is a potential method to prepare an affinity matrix. (C) 2013 Elsevier B.V. All rights reserved.