The invention discloses a power-grid frequency modulation control system and method with participation of an electric boiler. The control system comprises an electric boiler dynamic module, a generating system equivalence module and an electric boiler frequency response module; according to a backwater temperature and a heating power sampling value of present time, the electric boiler dynamic module calculates the average water body temperature of the electric boiler of next time, and transmits the average water body temperature to the electric boiler frequency response module; the generating system equivalence module obtains the system frequency fluctuating condition according to the load state as well as a rotor motion equation; and according to the system frequency fluctuating condition, the electric boiler frequency response module determines whether to participate in frequency modulation of the system, calculates the frequency modulation potential of the electric boiler according to the received average water body temperature of the electric boiler of next time, and adjusts the heating power of the boiler according to the frequency modulation potential of the boiler and enables the electric boiler to participate in system frequency modulation control. Thus, the control system changes the load of the electric boiler, adjusts the power rapidly, and keeps a balance between the generating power and the load demand.