Abstract: Based on the chip-on-board(COB) packaging LED chip, the thermal resistance model of LED was analyzed,and the substrates temperature when the junction was working at the ideal temperature was deduced. For the heat dissipation problem existing in the high-power LED, a fuzzy controller based on the double-in and double-out water jet cooling system developed by the research group was designed. The temperature change and temperature change rate were chosen as the inputs of the controller,and their ranges were described. According to the designed controller, programs were written and downloaded to the control chip. Through experiment under the environment temperature being 20℃, the LEDs substrate temperature is between 35.5℃ and 36.5℃, which ensures the light working stable. It provides a controller design for high-power LED heat dissipation system and has some practical significance.