The invention discloses a photovoltaic power generation equipment fault current online calculation method and device. The invention provides a photovoltaic power generation equipment fault current online calculation method. Calculation only needs to be carried out based on electrical information at two ends of a line. Iterative calculation is not needed in the calculation process, for a photovoltaic power generation unit power distribution network with high permeability and scattered access, the calculation time can be remarkably shortened, the real-time performance is higher, and the technical problems that an existing photovoltaic power generation unit fault analysis method is long in calculation time, and the requirement for high real-time performance of a power grid fault analysis taskis difficult to meet are solved.