An electron emission display and a driving method thereof, where a brightness is adjusted differently according to a brightness of a frame in order to reduce power consumption and prevent a brazing fire from occurring, and to easily recognize a change of the brightness. The display includes a pixel portion adapted to receive a data signal and a scan signal, the pixel portion being further adapted to display an image, a data driver adapted to generate the data signal using video data, the data driver being further adapted to transfer the data signal to the pixel portion, a scan driver adapted to transfer the scan signal to the pixel portion, a timing controller adapted to transfer a drive signal to the data driver and to the scan driver, the drive signal driving the data driver and the scan driver, a data processor adapted to generate a control signal corresponding to frame data obtained by summing a size of video data input during one frame and a power supply section adapted to generate a drive power source and transfer the drive power source to the pixel portion, the data driver, the scan driver, the timing controller, and the data processor, wherein a brightness of the pixel portion is varied according to the control signal, and an amount varied of the brightness is determined based upon the size of the video data during the one frame.