A control apparatus and a combiner box are provided. In a case that component maintenance needs to be performed, an optimizer connected to the combiner box is controlled to operate in a safe mode, and a switch-off signal is outputted to disconnect the combiner box from an inverter if an output current of the combiner box is smaller than a threshold. In a case that the maintenance is completed, the optimizer connected to the combiner box is controlled to operate in a maximum power point tracking mode, and the combiner box is connected to the inverter if an input voltage of the combiner box is greater than an output voltage of the combiner box, that is, if an output voltage of a corresponding string increases gradually to a value exceeding a direct current bus voltage.