The invention relates to the field of power monitoring technologies and particularly discloses a direct-current looped network online monitoring system and method. The monitoring system comprises a bus I, a charger circuit I, a storage battery circuit I, a bus II, a charger circuit II, a storage battery circuit II, a buscouple circuit, a buscouple switch, a voltage collection system and a currentcollection system, wherein the buscouple circuit is connected with the bus I and the bus II through the buscouple switch; the buscouple switch is provided with position auxiliary contacts used for collecting the opening and closing state of the buscouple switch; the voltage collection system is used for detecting voltages of the bus I and the bus II respectively; and the current collection systemis used for detecting currents of the charger circuit I, the charger circuit II, the storage battery circuit I and the storage battery circuit II respectively. Through the direct-current looped network online monitoring system and method, whether a direct-current looped network exists or not can be judged rapidly and effectively, so that discrimination efficiency and discrimination accuracy are improved, and stable running of a power grid system is guaranteed.