This application provides a flying capacitor charging method and apparatus, applied to a multi-level topology circuit, to provide a flying capacitor charging solution with a small occupation area and strong applicability. The circuit is connected to an input power source by using a first switch, and is connected to an output power source by using a second switch. A first end of a first capacitor in flying capacitors in the circuit is connected to a first electrode of a first semiconductor switch transistor, a second end of the first capacitor in the flying capacitors in the circuit is connected to a second electrode of a second semiconductor switch transistor, and a second electrode of the first semiconductor switch transistor is connected to a first electrode of the second semiconductor switch transistor by using a second capacitor. The second capacitor is an input capacitor, an output capacitor, or another flying capacitor.