The invention discloses a light-emitting device and an application of the light-emitting device to displaying notebook power. The light-emitting device comprises more than two light emitters and a control circuit, wherein the control circuit controls the light emitters to emit light; and the control circuit comprises a controller, a USB (Universal Serial Bus) interface and a control switch. The USB interface is connected with the controller, the controller controls the on and off of the control switch, and the control switch controls the on and off of corresponding light emitter loops. The battery power information of a notebook computer is stored into a USB register, the controller reads the battery power information from the USB register and converts the battery power information into delay time, the delay time is used as a time interval, all light emitters are sequentially lightened circularly, and the circulation speed of circular lightening of each light emitter is expressed as the battery power information. The light-emitting device has simple structure and convenience in use. The residual batter power of the notebook can be conveniently and visually displayed through the light-emitting device. The light-emitting device has the decorative function.