The existing microgrid operation schemes do not consider the dynamic performance of frequency?in the islanded operation of microgrids. When an islanded microgrid encounters a disturbance, the sudden power mismatch could impose security risks or even a system collapse. To address such a challenge, this paper proposes the primary frequency response rescheduling (PFRR) approach. For a certain operation interval, the PFRR will optimally reschedule the distributed generators (DGs) with non-zero mechanical inertia and adjust the battery power. And the objective is to limit the rate-of-change-of-frequency (ROCOF) and to maintain the post-disturbance frequency nadir above a prescribed threshold. The effectiveness of the proposed strategy is verified by a case study on the IEEE 123-node test feeder system and the time-domain simulation in MATLAB Simulink.