The invention discloses an accumulator battery online equalizing system which comprises a central processing controller, an electricity quantity acquisition module, a battery switching module, a voltage online equalizing module, an internal resistance and capacity online equalizing module and the like. The system can perform online and real-time equalizing adjusting on the voltage, the internal resistance and the capacity of a battery cell in an accumulator battery, can ensure that each battery in the accumulator battery is operated at an optimized operating state, greatly prolongs the operating life of the accumulator battery by more than two times, improves the reliability and the performance of the accumulator battery, reduces the environment pollution caused by the battery, and has good social benefit and environmental protection property; and the system adopting the active equalizing method can cancel the traditional equalizing method of periodic charging, reduces water loss of the battery, greatly reduces the probability of incontrollable low heat, prolongs the service life of the battery, simultaneously avoids the vulcanization of the battery, and saves a large amount of cost.