According to a vacuum failure auxiliary brake control system for an electric vehicle, the vacuum degree pressure value and the vacuum degree pressure value decreasing rate of a vacuum degree sensor are monitored in real time through a central controller, the fault level is judged according to the vacuum degree pressure value and the vacuum degree pressure value decreasing rate, and under the condition that a brake lamp switch is not triggered, in a certain data acquisition period, if the vacuum degree pressure value decline rate is greater than a set value 1, judging that the fault is a vacuum system air leakage first-level fault; in a certain data acquisition period, if the vacuum degree pressure value decline rate is greater than a set value 2, judging that the fault is a vacuum system air leakage secondary fault; and when the vacuum degree pressure value is smaller than the set value 4, the central controller judges that the vacuum system leakage three-level fault occurs, the central controller enters the state of preparing to start the vacuum failure auxiliary braking function, and meanwhile, a braking system fault lamp is turned on, a sound alarm is generated, and a fault code is recorded. According to the system, under the condition that the vacuum booster system fails, through logic setting of the central controller, the ESC and the motor driving system are cooperated to carry out braking and quit braking according to the intention of a driver, so that the driving safety is ensured.