A kind of voltage-controlled polarization controller made in electro-optic materials is studied in the experiment. By changing voltages added on the different plates, the corresponding out states of polarization are gotten which spread all over the Poincare . Results show that the phase retardation angle in each plate is a quadratic function of the applied voltages. And the degrees of polarization ellipsoids are obtained with the same the principal state of polarization. PC, a key element in the communication system, has great advantage for Polarization mode dispersion compensation and accurate controlling to the states of polarization.