A pixel driving circuit includes a first capacitor, a data input unit, a liquid crystal capacitor, a control unit and a driving unit. The first capacitor has a first terminal and a second terminal, wherein the first terminal is configured for receiving a first reference voltage. The data input unit is configured for inputting a data signal to the second terminal of the first capacitor according to a first scanning signal. The liquid crystal capacitor has a first terminal and a second terminal. The first terminal receives a first operating signal. The control unit is configured to control a voltage of the second terminal of the liquid crystal capacitor according to a second scanning signal. The driving unit is configured to control the voltage of the second terminal of the liquid crystal capacitor in response to the data input unit is disabled by the first scanning signal.