Platinum was employed as catalyst in fuel cell system but it was expensive and could not tolerate high carbon monoxide (CO) levels. If hydrogen gas containing with carbon monoxide is used, the fuel cell performance will be drastically reduced. Thus, platinum alloy catalyst was used as an anode in fuel cell application instead of pure platinum catalyst. In this research, the preparation of carbon-supported platinum/ruthenium catalysts (PtRu/C) by electroless deposition was studied for using as an anode in PEM fuel cell. The studied parameters were atomic ratio of Pt:Ru, carbon-supported improvement, concentrations of metal precursor, types and concentrations of reducing agents. Physical and electrochemical characterization of prepared PtRu/C catalysts were determined by X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), polarization, cyclic voltammetry (CV) and impedance spectroscopy. The results showed that the optimum condition for PtRu/C catalyst preparation was 1:0.5 of Pt:Ru atomic ratio on carbon-supported that improved by acid solution, 10 and 10 g/l of hexachloroplatinic acid (H2PtCl6) and ruthenium chloride (RuCl3) solution, respectively, 0.15 M of formic acid as reducing agent. PtRu/C catalyst prepared from the optimum condition was examined the performance of CO tolerance in PEM fuel cell. It was found that PtRu/C catalyst was tolerant to CO better than Pt/C catalyst.