The invention discloses a plug-in hybrid vehicle high-voltage control device and a high-voltage powering-on method thereof, and belongs to the technical field of plug-in hybrid vehicles, and technicalproblems that a conventional plug-in hybrid vehicle controller is low in reliability and high in cost are solved. The high-voltage control device includes main source positive and negative pole interfaces, auxiliary source positive and negative pole interfaces, a first contactor, a power assembly current transforming unit, a conventional component current transforming unit, and a conventional component power distribution unit. The main source positive pole interface is connected with one end of the first contactor. The power assembly current transforming unit is connected between the other end of the first contactor and the main source negative pole interface, and is used to transform current for high-voltage electric power transmitted between a power assembly component and a main source.The conventional component current transforming unit is connected between the auxiliary source positive and negative pole interfaces, and is used to transform current for high-voltage electric powertransmitted between a conventional component and the main and auxiliary sources. The conventional component power distribution unit is connected between the auxiliary source positive and negative poleinterfaces, and is used for the auxiliary source to transmit high-voltage electric power to the conventional component.