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The reliability problem must be solved for achieving large-scale application about LEDs, and the temperature is a key factor to affect LED reliability. In order to find the temperature effects on the module of high-power light emitting diodes (LEDs), a finite element approach was used to study the reliability problems of LEDs under high temperature and low temperature. A thermal shock experiment of LEDs was conducted by thermal shock chamber. The numerical simulations were used to obtain the thermal stress distribution of the LED modules. The simulated results showed that the stress generated at interfaces of all kinds of materials is relatively large comparing to the other parts in LED. After the thermal shock test, the rate of LED failure is 4%. The reasons of failure are high junction temperature of chip, materials degradation, thermal mismatch of materials, delamination and so on. Base on the above simulations and experiments, failure mechanisms were analyzed. These conclusions provide a basis for further study of the reliability of the LED under temperature loading. At the same time it provides a foundation for designing the package reliability about LED modules

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