The invention discloses a battery management system and a battery management method. The system comprises a battery pack, sub-string battery management systems and a general battery management system, wherein the battery pack is formed by parallel connection of a plurality of sub-string batteries; each sub-string battery is formed by connecting a plurality of single batteries in series; the quantity of the sub-string battery management systems is the same as that of sub-strings; two lead wires are led out from each connection point of the single batteries in each set of the sub-string battery, wherein one lead wire is directly connected with the sub-string battery management systems and the other lead wire is connected with the sub-string battery management systems through a thermistor; and the general battery management system is connected with the sub-string battery management system and a control system of an electric automobile. According to the battery management system and the battery management method, temperature and voltage faults can be found in the shortest time, damages and fire breakout on the battery pack can be avoided, and the safety performance of the battery pack is remarkably improved.