A display device and an operation method thereof are provided. The display device includes a frame scaler, a timing controller, a LCD panel and a source driver. The frame scaler provides a plurality of image data according to an image signal and determines whether the image data are repeatedly transmitted according to a frame control signal. When the image data are repeatedly transmitted, the image data transmitted firstly are set to correspond to gray scale data, and the image data retransmitted are set to correspond to a display image transmitted by the image signal. The timing controller receives the image data to provide a plurality of image display data and receives the frame control signal to determine a data transmission rate of the image display data. The source driver provides a plurality of display voltages to the LCD panel according to the image display data.