A multi-phase buck converter comprising a first switch set, a second switch set, a capacitor, a first power storing and coupling unit, and a second power storing and coupling unit is provided. The first and the second switch sets are for providing an input voltage and a low voltage. One end of the capacitor is coupled to the low voltage, and the other end generates an output voltage. The first and the second power storing and coupling units are respectively coupled between the capacitor and the first switch set and between the capacitor and the second switch set. The first power storing and coupling unit comprises a primary coil and a first inductance. The second power storing and coupling unit comprises a secondary coil and a second inductance. During a first, a second and a third period, the first inductance and the second inductance respectively store, release, and store power.