An effective thermal design of light- emitting diode (LED) packaged with low thermal resistance is critical to improve the performance of LED.A cop per/water unit loop heat pipe (LHP) heat sink is designed.The thermal capabilities,including start-up performance,tem perature uniformity and thermal resistance,are investigated experimentally at the conditions of differe nt heating methods,filling ratios,wind pressures,and incline angles.The obtained results indicate that the start time of the loop heat pipe is about 6.5min with the input power of 30W;the thermal resistance of the loop heat pipe is in the r ange of 0.48－1.62K/W;when the heat load is 30W,the temperature of the evaporator can be controlled steadily under 75℃;the difference of surface temperature of the evaporator is controlled nearly under 1.6℃,and the junctio n temperature is at the minimum when the filling ratio is about 60%.Within a certain range of the wind pressure (les s than 130Pa),the more the wind pressure is strengthened ,the more the heat dissipation of LED products can be i mproved.