The decatungstodivanadogermanic heteropoly acid H6GeW10V2O40.22H(2)O was synthesized for the first time by the stepwise acidification and the stepwise addition of solutions of the component elements. The optimal proportion of the component compounds and the pH of the synthesis reaction are given. The product was characterized by means of inductively coupled plasma (ICP), IR, UV, X-ray diffraction and thermal analysis. The IR, UV and XRD indicate that H6GeW10V2O40.22H(2)O possesses the Keggin structure. The results of ac impedance measurement show that its proton conductivity is 1.20 x 10(-2) S cm(-1) at room temperature (16 degreesC. (C) 2004 Elsevier Ltd. All rights reserved.