The present invention discloses a man-machine interface control device and method. The man-machine interface control device comprises a temperature detection module, a comparison module and a control module, the temperature detection module acquires the face temperature at each preset time interval and transforms the face temperature into a corresponding initial voltage signal, the comparison module carries out the amplification and the voltage stabilization processing on the initial voltage signal and then compares the initial voltage signal with a preset reference range, and the control module controls the backlight brightness of a man-machine interface according to a comparison result. According to the present invention, the backlight brightness can be adjusted properly according to an actual watch distance, the improper backlight brightness can be prevented from influencing a display effect, and the harm to the eyes is reduced.