The invention discloses a method for predicting distributed photovoltaic power. The method comprises the steps that firstly, a region range where a distributed photovoltaic power station to be monitored is located is determined; secondly, solar radiation values in the region range are detected in a unified mode, so that the phenomenon that power of each power station is independently detected in the prior art is avoided; thirdly, the problems of cost waste caused by accumulation and the low detection accuracy caused by an accumulation error are solved. The solar radiation values detected in the unified mode are uploaded to a main photovoltaic operation monitoring and controlling station, so that data obtained by the main monitoring station are more accurate and the method and system accord with the actual condition.