A multi-phase power controller is adapted for operating N power channels and is coupled to M drivers and an external system. The M drivers respectively have an enabling pin, and the multi-phase power controller includes a power state pin and M control pins. The power state pin is coupled to the enabling pin of each of the M drivers and the external system. The M control pins are coupled to the M drivers. In a power start period of the multi-phase power controller, the number of the power channels operated by the multi-phase power controller is less than N. After the power start period, the multi-phase power controller enables the M drivers through the power state pin and notifies the external system that a power start procedure has been completed through the power state pin.