The invention discloses a motor's low voltage protection method and an apparatus, comprising: when a power grid voltage is reduced, after a first preset time, comparing the motor terminal voltage with the locked-rotor voltage; if the motor terminal voltage is smaller than the locked-rotor voltage, then, tripping; after a second preset time, conducting switch closing again; then, comparing the motor terminal voltage with the locked-rotor voltage again; if the motor terminal voltage is greater than the locked-rotor voltage, starting the motor; and if the motor terminal voltage is smaller than the locked-rotor voltage, stopping the motor. According to the invention, the method and the apparatus are able to cut off a motor that cannot work normally so as to protect the stable operation of other motors and the power grid.