Vehicle power management system and power management method thereof

The invention discloses a vehicle power management system and a power management method thereof, and the power management method comprises the steps: when a microcontroller receives a switch closing signal, the microcontroller judges whether the voltage of the switch closing signal is lower than a voltage threshold; when the voltage of the switch closing signal is lower than the voltage threshold, stopping using the vehicle-mounted power supply to supply power to the standby battery and using the vehicle-mounted power supply to supply power to the rear-end load; starting a counter of the microcontroller; when the counting time of the counter reaches a first time threshold, stopping using the vehicle-mounted power supply to supply power to the rear-end load and using the standby battery to supply power to the rear-end load; when the counting time reaches a second time threshold, the microcontroller transmits an electric switch closing signal to a rear-end load; and when the counting time reaches a third time t