A series of sulphonated poly (ether ether ketone) (sPEEK) membranes for direct methanol fuel cells are successfully prepared under different humidity degree conditions. These membranes exhibit enhanced proton conductivity at high humidity degree. It is proved that the different proton conductivity is ascribed to the orientation arrangement of sulphonic acid groups, which is caused by environmental water in the preparing process of membranes. A model is established by analyzing the dynamics of membrane formation and proved by Field emission scanning electron microscopy (ESEM) and X-ray photoelectron spectroscopy (XPS). (C) 2009 Professor T. Nejat Veziroglu. Published by Elsevier Ltd. All rights reserved.