Abstract: High junction temperature of LED has been the technical bottleneck of the development of high power LED. With the rising of heat flux density, the simple straight fin heat sink can not meet the requirement of heat dissipation in natural cooling conditions. We set up a heat dissipation system based on the heatpipe technology, analyzed the heat transfer mechanism and the route of heat dissipation ,then established the model of thermal network according to the physical model and calculated the thermal resistance of each part, finally got the total theoretical thermal resistance and the LED junction temperature. At the same time, we made a simulation analysis of this heat dissipation system by using the finite element method. Simulation results of the LED module(0.025 m0.025 m0.005 m) with 30 W input power show that the junction temperature of LED stable is at 58.19℃, less than 65℃ which is the deadline of requirement. The cooling system applying the heat pipe meets the requirement of design well. The theoretical junction temperature calculated by thermal model is 57.43℃,only 0.76℃ less than the simulation result, implying the error is only 1.31%,this validates the theoretical analysis calculation ,which has guiding significance for practical engineering design.