Heat dissipation is a key issue in the application of high-power LEDs,as it has significant influence on the output power and lifetime of the device.In this work,finite element method(FEM) is adopted to determine the temperature distribution in 1 W high-power white LEDs.The simulation results show good agreement with the experimental data.The thermal limit of the available package is also studied.The influence of chip-size on the junction temperature has been studied.The maximum input power and chip-size under certain design requirement are also given.This method offers great ease in estimating the temperature distribution and thermal limits of the package.