A common voltage compensation device suitable for a display panel of a liquid crystal display is provided. The common voltage compensation device includes a timing controller and a compensation circuit. The timing controller receives an image signal and generates control signals to the compensation circuit according to a determination mechanism. The compensation circuit sends a common voltage compensation signal to the display panel according to the control signals outputted from the timing controller in order to compensate the common voltage on the display panel. The determination mechanism performs an analysis of a gray scale distribution of a horizontal line signal of the image signal, and determines whether to compensate the common voltage according to an analysis result, and determines a polarity required to be compensated to perform the compensation when the compensation is needed.