The invention discloses a frequency fluctuation analysis method and system under the commutation failure impact of an asynchronous networking system. The method comprises the following steps that: obtaining the relevant data of the sending end and the receiving end of an asynchronous networking direct-current system in real time from an EMS (Energy Management System), and carrying out formatting processing on the data obtained in real time; and adopting an improved simplified analysis model to analyze frequency fluctuation under the commutation failure impact of the asynchronous networking system so as to quickly estimate the sending end frequency increasing range and the receiving end frequency decreasing range of the asynchronous networking direct-current system. By use of the method, the improved simplified analysis model is adopted, the equation of motion of a motor rotor is taken as a basis and is combined with the real time data of the receiving end and the sending end of the asynchronous networking direct-current system to quickly estimate the sending end frequency increasing range and the receiving end frequency decreasing range of the asynchronous networking system under the commutation failure impact, and an effective basis is provided for subsequent high circumferential cutting machine parameter setting and low-frequency load shedding setting operations. The method can be widely applied to the technical field of power grids.