The present application relates to a method and apparatus for adjusting the brightness of a display, and a display system. The method for adjusting the brightness of a display comprises: acquiring a brightness adjusting signal, wherein the brightness adjusting signal includes a position value indicative of a desired brightness of the display; comparing the position value with a first threshold, wherein an adjusting scale is defined according to a variable range of transparency of an object displayed on the display if the position value is smaller than the first threshold; generating a brightness value of the object according to the position of the position value in the adjusting scale; and applying the brightness value to the object displayed on the display. The method can adjust the transparency of the displayed object through the graphical system in an electronic device, thereby further lowering the brightness of the display.