An on-line accumulator monitoring system comprises the following modules: a battery module which is used for providing electric power; a voltage acquiring module which is used for acquiring the voltage of the battery module; a data processing module which is used for processing signals from the voltage acquiring module; and a data transmission module which is used for transmitting the signal from the data processing module. When the structure provided by the utility model is adopted, the on-line accumulator monitoring system can accurately detect the voltage of the battery. After the battery fails, alarm information is transmitted to outside through the data processing module, thereby facilitating in-time processing by related personnel.