The frequency fluctuation of the isolated network under disturbance is within a certain range, which is an important condition for the stable operation of the isolated network. In this paper, the influence of the zero-pole distribution on the peak value of the frequency offset is analyzed for the isolated network with high-order speed control system, and the estimation expression of the peak value of the isolated network frequency offset is given. On this basis, using the method of eigenvalue sensitivity, the sensitivity amplitude and phase of zero pole to governor PI, speed measurement time constant, power feedback time constant, load feed-forward coefficient and modulation coefficient are calculated. The influence relationship of governor parameters on the frequency offset peak is revealed. The governor parameter optimization scheme for reducing the frequency offset peak value and the parameter adjustment suggestion for ensuring the stability of the isolated network frequency are proposed and verified by PSCAD/EMTDC electromagnetic transient simulation software. This work is supported by Fundamental Research Funds for the Central Universities (No. 2018ZD01).