A self-light-up decorating lamp, comprises a decoration body; and an illumination device installed to the decoration body; the illumination device including a solar plate, a battery, an LED lamp set, a light-sensitive resistor, a switch and a LED lamp set; the solar plate being installed at an outer side of the decoration body for receiving solar or other light energy to convert the energy into electric energy; one end of the battery being connected to the light-sensitive resistor and the switch; one end of the switch being connected to the LED lamp set and the LED lamp set is installed on the decoration body. The decoration body has a form selected from an advertise board, an indication board, an announcement board, and a display board. The solar plate receives electric energy which is converted from solar or light energy. The light-sensitive resistor serves to actuate the LED lamp set.