A cooling system of an LED light employs a dehumidifying agent absorbing moisture in the air while the LED light is turned off, and dissipates heat from the LED light using heat of vaporization by vaporization of the moisture by heat from the LED light when the LED light is turned on. The system includes an LED module, a thermal sheet, a heat pipe, a heat sink, and a dehumidifying sheet. The LED module includes a PCB and multiple LEDs, and the thermal sheet is disposed on the LED module. The heat pipe of a cornered U-shape has a circular cross section and is coupled to a connector on the thermal sheet. The heat pipe has a horizontal section contacting an upper side of the thermal sheet and a vertical section protruding to the connector. The dehumidifying agent is disposed on the heat sink inserted into the heat pipe.