The utility model relates to a discharge control device of lead-acid battery, which comprises a lead-acid battery and an electromotor as well as a control circuit and a warning circuit. Through the control circuit electric motors the lead-acid battery supplies the electromotor power. The control circuit monitors the discharge depth of lead-acid battery at real time and sends control signal when the discharge depth of lead-acid battery reaches a certain predetermined value, then the warning circuit sends warning information. The control circuit monitors the discharge depth of lead-acid battery at real time, when the discharge depth of lead-acid battery reaches a certain predetermined value the warning circuit will send warning information to remind the user of charging in time, thus the lead-acid battery will be avoided over discharging which will prolong the discharge depth.