The organic silica with thiol group/Nafion (R) composite membranes were prepared by casting method using various additives including HS(CH2)(3)CH3Si(OCH3)(2) (SH-), tetraethyl orthosilicate (TEOS) and HS(CH2)(3)CH3Si(OCH3)(2)-TEOS (HS-TEOS) in Nalion (R) solutions. All composite membranes had an adulterated content of 5 wt.%. SEM experiments indicated evenly distributed particles within all the Nafion (R) composite membranes. The properties of the composite membranes in terms of methanol permeability, proton conductivity, and cell performance were evaluated by single cell of direct methanol fuel cell (DMFC). The 125 mu m SH-TEOS/Nafion (R) composite membranes showed about 50% decrease of methanol crossover compared with the commercial Nafion (R) 117 membrane. The proton conductivity of the membrane lowered slightly compared with that of Nafion (R) 117. The SH-TEOS/Nafion (R) membrane was more suitable for DMFC of high concentration methanol than pure Nafion (R) membrane. (c) 2006 Elsevier B.V. All rights reserved.