A multi-stage buck converter is provided. The multi-stage buck converter includes a capacitor string, a power switch module and a power conversion module. The capacitor string includes N capacitors connected in series. The power switch module is coupled to the capacitor string and includes N power switch groups. The power conversion module is coupled to the power switch module and includes an energy storage element. Wherein a working frequency of the power conversion module is equal to N times of the switching frequency of each of the N power switch groups, and N is a positive integer greater than or equal to 2. Wherein the working frequency is the number of times of the energy storage element that completes charging and discharging in a unit time.