The invention provides an emergency power supply device realized by utilizing silicon controlled rectifier technology. A battery pack is a storage battery; the storage battery is charged constantly through a charger, and keeps a floating charge state gradually with the rise of voltage, so that a standby DC power supply is formed; once no commercial power AC input is detected, a quick switch switches on immediately; a storage battery power supply transmits power to a DC output end automatically through the quick switch, and the voltage at the DC output end no longer reduces; and when the commercial power AC input returns to normal, the quick switch switches off, and meanwhile, the charger charges the storage battery additionally. The emergency power supply device can reduce the accidents caused to equipment by power failure, thereby ensuring equipment and personal safety.