The invention relates to a mobile substation in the substation field. The mobile substation comprises a high-voltage power transformation vehicle and a medium-voltage power distribution vehicle. The medium-voltage power distribution vehicle is equipped with a medium-voltage switchgear, secondary devices, secondary device accessories and a carrier for allowing the secondary devices/ the secondary device accessories to be mounted. The medium-voltage power distribution vehicle is equipped with a prefabricated cabin. The medium-voltage switchgear, the secondary devices, the secondary device accessories and the carrier are arranged in the prefabricated cabin. The carrier is formed by secondary device mounting racks arranged in the prefabricated cabin; and the secondary device and the secondarydevice accessories are arranged up and down on the secondary device mounting racks. Compared with the prior art, the electrical components are arranged in the prefabricated cabin, so that the electrical components can be protected better, and integration degree of the medium-voltage power distribution vehicle is higher. Besides, the secondary devices in the prefabricated cabin are arranged vertically, so that height space of the prefabricated cabin is utilized fully, the volume of the prefabricated cabin is allowed to be more compact, and the medium-voltage power distribution vehicle is allowed to walk conveniently.