The invention provides a charger detection device for a battery protection cascade system. The charger detection device comprises N battery protection chips which are in one-to-one correspondence connection with N battery strings, wherein the first battery protection chip is a master chip and the rest battery protection chips are cascade chips; the N battery strings are connected in series, and respectively comprise M batteries, and N and M are natural numbers more than or equal to 2; each battery protection chip comprises a grounding end, a power end, a master and slave chip select signal end and a charger detection port; a connecting point of the power end of the Nth battery protection chip and the positive terminal of the Nth battery string is extracted to form the positive end of a battery pack, a connecting point of the grounding end of the master chip and the negative terminal of the first battery string is extracted to form the negative end of the battery pack, and a charger is connected between the positive end and the negative end; and the charger detection port of the master chip is connected to the negative end of the battery pack through a port resistor, the voltage of the battery pack is detected, and the connecting state of the charger is judged. The charger detection device can safely and reliably detect the connecting state of the charger, transmit an overvoltage hysteresis control signal to the cascade chips, and improve the safety of an application system.