Abstract: The thermal model of phosphor conversion white LED (pc-LED) is the basis of LED heat dissipation design. The commonly used single heat source single heat dissipation channel thermal model can not express the real heat dissipation state of pc-LED. The existing dual heat source dual heat dissipation channel thermal model requires T3ster and infrared thermal imager to measure model parameters, and the heat generation phenomenon of epoxy adhesive radiated by blue LED is ignored. Therefore, the method of directly measuring the junction temperature of PC LED chip with PT100 chip and directly measuring the phosphor temperature with micro thermocouple is proposed. According to the experiment, the dual heat source dual heat dissipation channel thermal model is improved, the thermal resistance and heat flow values are calculated, and the real heat dissipation state of pc-LED is revealed, and the direct measurement method and improved model are verified, and the useage of expensive instruments such as T3ster and infrared thermal imager is avoided, The experiment also find that the pure epoxy adhesive also has heat generation phenomenon radiated by blue LED.