The isolated network operating mode of the existing microgrid, in order to improve the frequency stability of the microgrid. a circulating system is made up of a proton exchange membrane fuel cell (PEMFC), a water electrolysis device and a hydrogen storage device to realize frequency modulation without difference.. At the same time, the improved droop control strategy considering the SOC of battery is involved in the primary frequency regulation. The control strategy of the battery pack and PEMFC cycle system in frequency modulation is also proposed. The calculation and simulation shows that the PEMFC cycle system and the FM control strategy using the dynamic droop coefficient can quickly realize the primary frequency modulation and two frequency modulation of the microgrid.