A power supply control method and a monitoring system configured to implement the power supply control method are provided. The monitoring system includes a base station, a drone, and a processor. The base station includes a charging device. The charging device includes a power supply connector and a power source coupled to the power supply connector and outputting electric power through the power supply connector. The drone includes a battery configured to provide electric power to the drone and a charging connector configured to connect the battery and the power supply connector. When the charging connector is connected to the power supply connector, the processor determines an abnormal situation on the power supply connector or the drone according to an electrical characteristic during charging the battery by the power source. The abnormal situation is associated with a foreign object formed on the power supply connector or the drone.