The invention discloses a regional equivalence based distributed photovoltaic output prediction method and system. The method comprises that distributed photovoltaic power stations in a region are clustered and analyzed according to geographic positions and sun radiation characteristics, and are equivalent to virtual centralized photovoltaic power stations; and according to power of the virtual centralized photovoltaic power stations, the total power of the distributed photovoltaic power station is calculated. The system comprises an equivalence module and a power calculation module. Via the method and system, the geographic positions and sun radiation characteristics of the distributed photovoltaic power stations can be combined, the power generation power of the distributed photovoltaicpower station can be calculated more reasonably according to data of meteorology monitoring equipment in the region, collected data is more accurate, the distributed photovoltaic power stations can beclassified and equaled reasonably, and thus, the output condition of the distributed photovoltaic power station can be predicted reasonably and more accurately.