The invention relates to a mobile emergency power supply system and a work method thereof. The system comprises an emergency power supply vehicle and an emergency feed line power supply vehicle, the emergency power supply vehicle is provided with a battery system, a charging device, a DC converter, a DC monitor and a communication management unit, the battery system comprises an energy storage battery and a battery management unit, 220V AC is connected to input of the charging device, three paths of output of the charging device are (electrically) connected with the energy storage battery, theDC converter and an aviation plug respectively, two paths of output of the DC converter are electrically connected with the battery management unit and the aviation plug respectively, the communication management unit is in communication connection with both the DC monitor and the battery management unit, the DC monitor is in communication connection with the charging device and the DC converter,and the emergency feed line power supply vehicle is provided with feed line switches. The system is suitable for different work scenes, the device utilization rate is improved, movement and configuration are flexible, and use is easy.