CMK-5 supported Pt nanoparticles were prepared by a modified microwave-irradiated polyol process. In order to improve the dispersion of Pt nanoparticles, cetyltrimethyl ammonium bromide (CTAB) as stabilizer was added to the microwave heating process. The effects of CTAB on structural and electrochemical properties of Pt/CMK-5 were investigated. It was found that the addition of CTAB facilitated Pt nanoparticles to disperse on the carbon surface. Cyclic voltammetry in sulfuric acid showed that Pt catalyst prepared with CTAB in the microwave synthesis displayed higher peak current and larger electrochemical active surface area than the commercial catalyst Pt/C (E-TEK).