A series of Prussian blue(PB) modified Pt electrodes with various layers were prepared by electrostatic layer-by-layer adsorption of iron（Ⅲ）and hexacyanoferrate（Ⅱ）on Pt electrodes. Scanning electron microscopy（SEM）and UV-visible spectroscopy（UV-Vis）were used to observe their morphologies and optical properties，while the electrochemical properties were determined by cyclic voltammogram（CV）.The results showed that the nano-size PB film could be self-assembled on the Pt electrodes with a controlled thickness，and the UV-Vis absorbance was linear with the dipping cycles. Both soluble and insoluble Prussian blue were the components of the film. The cyclic voltammograms showed that the peak current was in proportion to the square root of scan rate and the concentration of PB. The as-prepared modified electrodes can be used as biosensors.