The utility model discloses an electric power test truck with a tail board expanded type carriage for a high-voltage test platform. The electric power test truck with the tail board expanded type carriage for the high-voltage test platform comprises a carriage which is mounted on a truck body, the carriage comprises a fixed carriage body, a movable carriage body and a tail board, the fixed carriage body is fixed on the truck body, the movable carriage body capable of moving front and back along the truck body is mounted on the truck body, the rear end of the truck body is connected to the lower end of the tail board through a hinge, a hydraulic cylinder used for folding and unfolding the tail board is arranged at the connecting position of the tail board and the truck body, and electric supporting legs are arranged on the outer side face of the tail board. Through the mode, the electric power test truck with the tail board expanded type carriage for the high-voltage test platform is simple in structure, practical, convenient to operate and capable of guaranteeing precision of test data, overcoming disperstiveness of field connection and improving operating and using efficiency.