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Light emitting diodes (LEDs) are now widely used in many fields including traffic lights, vehicle backlights and liquid crystal display (LCD) displays because of their long life, good illumination efficiency and low energy consumption. At present, LEDs are increasingly replacing the traditional lighting and are being used in general illumination such as the street lamp. For the high-power LED street lamps, good light extraction is the most important thing, but low junction temperature of the LED modules is also critical for achieving a long lifetime and a high optical efficiency. Actually, there have been many reports about early failures of street lamps, called dead lamps that have been regarded as a barrier in the public and administration acceptance of LED street lamps. Therefore temperature estimation is always a crucial issue for LED product development. A multi-chip spreading thermal resistance model was applied to estimate the temperature distribution of LED street lamp. The experiment was first done to obtain temperatures of several locations in a prototype LED street lamp. Then the multi-chip spreading resistance model was established to calculate the full temperature distribution. Comparison between the model calculation and experimental measurement showed a good agreement, which demonstrates that the present model can be used in engineering design to estimate the temperature distribution of high-power LED street lamps.