The electrodeposition of cuprous oxide (Cu2O, red copper oxide) on Pt cathode in a weak acidic electrolyte was executed by the current modulation method. The formation mechanism of Cu2O was investigated by electrochemical characteristics analysis utilizing electrochemical quartz crystal microbalance (EQCM), chronopotentiometry (CP), and pulsed current methods. A scanning electron microscope and X-ray diffractometer were also used for investigation of the mechanism for Cu2O film growth. EQCM and CP results indicate that the dissolution potentials of Cu and Cu2O were different and were used for the selective dissolution of copper when the pulsed anodic current was applied. Pulsed electrodeposition technique offered a useful method in preparing Cu2O thin film, in which both Cu metal and Cu2O phases were electrodeposited on platinum electrode, when a higher cathodic current, -5.0 mA/cm(2), was constantly applied in a 10 mM copper nitrate solution. The cycling of current led to the rapid formation of a single phase of Cu2O thin film, which was uniform and compact.