Buck converter output port voltage is easily affected by system parameter change and thus reduces energy transmission quality. To deal with this, this paper puts forward a linear active disturbance rejection control strategy combined with a fuzzy reasoning mechanism. First, a discrete mathematical model is established to establish that the Hopf bifurcation disturbance is the cause of the low-frequency oscillation of the output voltage, and the necessary and sufficient conditions for its stability are analyzed by the frequency domain method. The existence of Hopf bifurcation disturbance is proved and verified by simulation. Second, based on theoretical analysis, fuzzy reasoning rules are designed, and then the rules are combined with error feedback control to improve the Hopf bifurcation disturbance rejection effect. The stability of the control strategy under the Hopf bifurcation disturbance and the limit of the observation error of each state to the disturbance are analyzed using the frequency domain method. Finally, through simulation analysis under different working conditions, Hopf bifurcation disturbance suppression is compared by using the control strategy and the traditional PI control strategy respectively. The results show that the proposed fuzzy linear ADRC strategy can effectively suppress the Hopf bifurcation disturbance and ensure the working performance of a Buck converter.