Abstract: Aiming at the problem of hysteretic nature existed in the primary frequency regulation of the generator unit based on the feedback control law after large power deficits, an event-driven fast frequency response（EFFR） control method is proposed. First,the connotation of EFFR is elaborated, of which the system architecture and operation scheme are designed. The specific disturbance event signals are used to trigger the emergency control mode and adjust the output of generator units promptly. Then,an extended system frequency response model is established to extract the coupling relationship among the disturbance power,EFFR power and the under-frequency load shedding operation by the periodic pre-decision method, on which the required EFFR power of the system can be estimated in the preconceived accident scenario. Additionally, with the objective of minimizing the control cost, the required EFFR power is distributed optimally, and the control commands for response generator units are calculated. Finally, a case study is carried out to validate the effectiveness of the proposed method.