A new calculation method is adopted aiming at the dynamic charactetristic of a thermal induced micro-electromechanical system (MEMS) infrared radiation source. By calculating the temperature rise dependent on power supply time and power with different initial temperature, the modulation depth of radiation source under different pulse frequencies is quantitatively reckoned. This meathod is capable of calculating the dynamic characteristics with large modulation depth. The influence of power supply mode and material emissivity is discussed in detail. The results show that adopting constant voltage source obtains a shorter response time than by adopting constant current source or constant power source under the same saturated power condition, thus it is more advantageous for dynamic modulation characteristic improvement. Also, high emissivity material reduces the rise time without regard to other parameters change. Combining the calculated result, a test experiment is carried out to study the frequency response characteristic of a MEMS Pt thin film infrared source, and the experimental result fits the calculation well.