In this paper,high temperature current driving(HTCD) stress and high temperature storing(HTS) stress are applied to study the degradation and thermal characteristics of high power LEDs.The results show a larger light dimming of 40%-60%under temperature-current-combined stress,and only 10%-14% dimming under temperature-only stress,demonstrating more obvious influence of the current stress on LED′s lifetime.The junction-to-case thermal resistance has changed a little under both degradation methods,with a larger change under the temperature-current-combined stress.The change mainly happens in the die attachment layer of the power LED,i.e.,the silver layer.The reason is that the inhomogeneous spatial distribution of silver particles results in gaps in the bonding interface under the high temperature.