CO tolerance electrocatalyst of PtRu-HxMeO3/C is prepared by a composite support method, which overcomes evident shortcomings of other preparing methods. According to the result of XRD and TEM, the catalyst shows high dispersion and the HxMeO3 exists in amorphous form. The electrooxidations of CO on the catalysts have been investigated in cyclic voltammetry, in which PtRu-HxMeO3/C shows lower CO ignition potential according to hydrogen and CO spill over effects, and the bifunctional mechanism is proved to be strengthened for the involvement of HxMeO3. The CO tolerances of catalysts are compared according to the PEMFC single cell performance and anode polarization curves operated with H-2/50 ppm CO and H-2/100 ppm CO. (C) 2003 Elsevier Science B.V. All rights reserved.