The synthesis and characterization of the Pt nanoparticle catalyst for oxygen electrochemi- cal reduction have been studied in this paper. The catalyst was characterized by AFM, XRD and SEM. Electrochemical behavior of the oxygen reduction on the prepared electrode was investigated. A linear relationship between the limiting current and the concentration of O2 is obtained and the sensitivity is 381 nA ppm-1 when the O2 concentration is in the range 7 to 5010ppm.