Catalytic oxidation of glycerol with molecular oxygen to glyceric acid was performed in a base-free aqueous solution over Pt/MWNTs and Pt/AC catalysts. Pt/MWNTs was more active for the easier accessibility of Pt on the external wall of MWNTs, and the initial TOF reached 10.63 mmol min(-1)/mmol-Pt. The easier accessibility of glycerol to Pt particles on MWNTs was confirmed by Raman.