The present invention provides a control device and a combiner box. The module maintenance is required, an optimizer connected with a corresponding combiner box is controlled to operate in a safety mode, and disconnection signals are output when the output current of the corresponding combiner box is smaller than a threshold to switch off the connection between the combiner box and an inverter, so as to reduce the impact current of arc on the optimizer. After the maintenance is completed, the optimizer connected with the corresponding combiner box is controlled to operate in an MPPT mode, and when the input voltage of the combiner box is larger than output voltage of the combiner box and namely the output voltage of the corresponding string is gradually increased to exceed the direct current bus voltage, the connection between the combiner box and the inverter is closed so as to avoid the impact current caused by too large voltage difference between the direct current bus voltages when the combiner box accesses the inverter.