The invention discloses a wireless power transfer system sliding-mode control method based on a Buck link, the method comprising the following steps of S1, determining the optimal switching point andthe steady state point on a uC1-iL phase plane by using the output capacitor voltage uC1 and the freewheeling inductor current iL of the Buck link as detection objects; S2, determining the slope of asliding-mode line and the longitudinal-axis intercept according to the optimal switching point and the steady state point; S3, determining whether current limiting control is needed, and if so, adjusting the slope of the sliding-mode line; S4, determining whether load switching occurs, and if so, adjusting the longitudinal-axis intercept of the sliding-mode line; S5, obtaining the output capacitorvoltage uC1 and freewheeling inductor current iL in real time, and controlling the state of a switch tube in a Buck circuit according to the sliding-mode control strategy. The method can accelerate the dynamic response, shortens a dynamic process, limits the current overshoot by changing the slope of the sliding-mode equation, quickly restores the output voltage of the secondary side to an original state during load switching, and improves the robustness and adaptability of the control.