Prussian white (a reduced state of Prussian blue) was electrochemically deposited on a polycrystalline Pt electrode from an acidic solution of ferricyanide. Electrochemical measurements showed that the formation of Prussian white on platinum electrode was a self-terminated process. A compacted PB film can be formed by using both potential scanning and potentiostatic methods as confirmed by AFM measurement. In situ FTIR measurements were carried out to explore the formation mechanism. The new band arising at 2075cm−1 is assigned to the characteristic absorbance of CN of Prussian white, while the band at 2104cm−1 is due to the absorbance of CN of Prussian blue. A possible mechanism of electrodeposition of Prussian white was discussed.