Porous ultrahigh-molecular-weight polyethylene/SiO2 membranes were prepared by thermally induced phase separation (TIPS) with white mineral oil as the diluent and SiO2 as an additive. Influential factors, including extraction method, SiO2 content, and cooling rate, were investigated. The results suggest that the both porosity and pure water flux of the membranes by extraction of the solvent naphtha in the tension state with alcohol were the best among our research. With increasing SiO2 content, the porosity, pure water flux, and pore diameter increased. However, with excessive SiO2 content, defects formed easily. Moreover, SiO2 improved the pressure resistance of the membranes. The cooling rate directly effected the crystal structure. A slow cooling rate was good for crystal growth and the integration of the diluent. Therefore, the porosity, pure water flux, and bubble-point pore diameter increased with decreasing cooling rate. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 2817 2824, 2010