As the electric power of high-power light emitting diode (HP-LED) increasing, the challenge of heat dissipation is also becoming higher and higher. The heat which can′ t be dissipated from chip effectively will raise the junction temperature of the LED devices. High junction temperature will not only affect the optical power, flux and other performance of LED devices, but also decay the lifetime of device rapidly. Therefore,knowing the temperature rising rules of HP- LED devices well becomes the key to improve the reliability of devices. The effects of different drive current, different substrate temperatures and different packaging materials on thermal resistance of LED devices are studied. The results show with the increase of current or with the substrate temperature increases, the thermal resistance of LED devices trend to decline and then rise. The changes of thermal resistance of LED devices packaged by aluminum substrates and ceramic substrates are different. When the substrate temperature increases, the thermal resistance of LED devices interconnected by the Al substrate keeps declining because of the higher pn- junction temperature of the LED device. The tested results of the thermal resistance of LED devices interconnected by different materials show that the thermal resistance are obviously effected by the interconnect layer and the substrate.