A digital image processing program package was developed to calculate the porosity, pore diameter distribution, pore area distribution, and pore shape distribution of membrane surface by treating the SEM photos of membrane surface and cross-section. Different membranes were prepared and investigated in this experiment, including polyacrylonitrile (PAN), polyaryletherketone with cardo (PEK-C), polyarylethersulfone with cardo (PES-C), polysulfone (PSI), polyvinylidene fluoride (PVDF), and poly (phthalazinone ether sulfone ketone) (PPESK) membranes. Compared with the analysis results of IBAS I/II image analytical instrument (made in Germany), the porosity analyzed by our program package was larger, and the dispersion of distribution was wider. The porosity of membrane cross-section was also determined. The pure water flux (J) and rejection (R) of bovine serum albumin (BSA) of membranes were measured, and the results agree with those obtained from our program. In addition, the gelation front movement was measured using ImageJ program and our program package, respectively, and the results were further compared. (c) 2007 Published by Elsevier B.V.