A display system for calibrating a displayed image includes a monitor device and a calibration device. The monitor device is used for displaying a calibration interface when an image calibration process is performed. The calibration device is coupled to the monitor device for selecting a calibration mode through the calibration interface. The calibration interface includes at least one calibration mode. The calibration device selects and confirms the calibration mode from the at least one calibration mode by using at least one key.