Abstract: To guarantee the stable operation and to smooth the new-energy-caused impact on power grid,coal-fired power generation units need to adapt to the new environment and improve their frequency modulation flexibility. In this paper,we use Ebsilon simulation software to model a 660 MW ultra-supercritical double reheating unit. Based on this model,the frequency modulation characteristics of different frequency modulation modes,such as high pressure feeding water heater bypass frequency modulation,overload control valve adjustment and condensate throttle frequency modulation,are studied respectively to obtain their effects on the unit load and thermal performance. Their advantages and disadvantages of these three kinds of frequency modulation methods are compared and ranked respectively. Finally,some valuable suggestions for the use of the frequency modulation methods are given. The results show that: it is better to use the whole high pressure feeding water heater bypass frequency modulation when the load demand for the unit is higher,to use the condensate throttling frequency modulation when the economic performance requirement is higher,and use1/2 mixed high pressure feeding water heater bypass or the whole bypass when both the load demand and the economic performance demand are considered. At the initial stage of response,it is suggested to open the overload control valve to realize the fastest response.