The embodiments of the present disclosure disclose a relay holding circuit and a battery management system. the relay holding circuit may include: a high-voltage isolated power source, a power source driving module, and a microprocessor of a battery management system; the high-voltage isolated power source may be respectively connected to two electrodes of a battery pack, an output terminal of the power source driving module, the microprocessor, and a first terminal of a first switching device; an input terminal of the power source driving module may be connected to the microprocessor; the microprocessor may be further connected to a primary battery, the microprocessor may output a low-level signal to the power source driving module when the primary battery supplies power abnormally.