The preparation and electrocatalytic activity of polyaniline-poly (propylene oxide ) (PAN-PPO) modified by Pt particles (Pt/PAN-PPO) were investigated. Pt/PAN-PPO was characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Pt particles on PAN-PPO were in the nanometer range, and dispersed in a three- dimensional distribution on the surface of PAN- PPO film. Compared with polyaniline and glassy carbon modified with Pt particles under the same conditions, Pt/ PAN-PPO exhibited a high electrocatalytic activity for lysine oxidation.