The embodiment of the invention provides a photovoltaic combiner box and a method and device for installation analysis of defend and counterattack diodes of a photovoltaic combiner box. The method comprises: the reverse current IZDW and the work voltage UZDW of a shielded photovoltaic battery pack are obtained according to a U-I characteristic curve; the work voltage UW of the shielded photovoltaic battery pack is determined according to the reverse current IZDW; it is determined whether the difference of the work voltage UW and the work voltage UZDW is smaller than a voltage error amplitude limiting or not; and if the difference of the work voltage UW and the work voltage UZDW is smaller than a voltage error amplitude limiting, the minimum number of the defend and counterattack diodes when the reverse current passes through the reverse current verification. According to the invention, the minimum number of the defend and counterattack diodes requiring to be installed can be analyzed to reduce current flowing backwards in the combiner box, reduce the power consumption caused by the conduction pressure drop of the defend and counterattack diodes and improve the operation efficiency of the photovoltaic power generation system when the local photovoltaic module is shielded.