The invention relates to a fault detection device for a high-capacity battery energy storage system. The fault detection device comprises a battery information acquisition module and an MCU which areelectrically connected with each other, wherein the MCU is electrically connected with a storage module, a clock module, a wireless communication module, a control switch button, an I/O interface, a display screen, a warning module and a power supply interface. According to the method for detecting faults of a high-capacity battery system by using the fault detection device, one ends of detectionlines respectively used for detecting the power quantity, current, voltage and temperature of a battery are connected to the I/O interface, the other ends of the detection lines are respectively connected to the battery; the battery information acquisition module feeds back signals detected by the detection lines to the MCU, the MCU converts the signals into corresponding data information, displays the data information through the display screen and gives corresponding instruction information. The fault detection device has the advantages of convenient remote monitoring, convenient remote control, energy conservation, environmental protection, intelligentization and timely and effective data transmission.