Anhydrous proton conductive MHSO4-H4SiW12O40 (MHS-STA) composites were successfully synthesized using mechanochemical treatment. 80MHS center dot 20STA (mol%) composite, for example, showed very high anhydrous proton conductivity above 10(-3) S cm(-1) in a temperature range from 160 to 60 degrees C under ambient pressure. From the X-ray diffraction study, it was confirmed that the mechanochemical treatment induced chemical interactions via ion-exchange between M+ ion in MHS and H+ ion in STA. Furthermore, phase-transition of raw substances, such as melting, dehydration and superprotic phase-transition, was suppressed in mechanochemically synthesized MHS-STA composites, indicating that improvement of anhydrous proton conductivity for MHS-STA composites is caused by the changes in protic conduction behavior. (C) 2012 Elsevier Ltd. All rights reserved.