Plasma impedance and power consumption were measured by modified voltage-current method at different applied voltages on the substrate electrode. The results indicated that discharge current increases with the increase of applied voltage on the substrate electrode when the applied voltage of RF electrode is fixed. As a result, plasma impedance decreases. In addition, only a small part of power was used by the plasma and a large part of power was consumed on the matching network and cables. Through the analysis of plasma electrical properties, it was found that the deposition rate of thin films will be increased with the increase of applied voltage on the substrate electrode so long as there is enough silane.