A method of adjusting display brightness, a light-emission control circuit and a display device are provided. A method of adjusting display brightness is applied to an light-emission control circuit, where the light-emission control circuit is configured to generate an light-emission control signal configured to control a light-emission of a display device. The method includes: adjusting, in the case that a display brightness of the display device is not within a predetermined brightness range, a duty ratio of the light-emission control signal, to enable the display brightness of the display device to fall into the predetermined brightness range.