Abstract: In order to study the influence of pulse width and repetition frequency on the damage threshold of HgCdTe detector, finite element method was used to build 2-D model of HgCdTe infrared detector and the temperature field of laser irradiation detector was simulated. Damage threshold of single pulse laser of off-band and in-band was obtained from the range of 10ns to 1000ns. Measurement of damage threshold of all pulse width was hard. After simulation and calculation, the damage threshold formula from the range of 10ns to 1000ns was concluded. The results show that, single pulse laser damage threshold of off-band laser is 9MW/cm²~0.9MW/cm², and 150MW/cm²~15MW/cm² for in-band laser. And single pulse damage threshold has the negative exponential relationship with laser pulse width. And then, repetition frequency laser was used to irradiate detector with the same repetition frequency. The temperature accumulation effect and damages of large area are more likely to occur under long pulse laser irradiation, because pulse separation of long pulse laser is smaller than narrow pulse laser. The research is useful for studying stress field distribution、thermoplastic wave and laser protection.