The invention relates to a photovoltaic array fault diagnosis method and device based on spatiotemporal distribution characteristics. A photovoltaic output time component and a spatial component are calculated and obtained by a time and spatial distribution function for the photovoltaic array output starting from the historical operation data and the historical environment data of a photovoltaic power plant, the components are used as a training data set, a probabilistic neural network is trained by the training data set, a photovoltaic array fault diagnosis model is obtained, a time functionand a spatial function for photovoltaic branch output are established to effectively describe the distribution law of string current under different fault conditions, the photovoltaic power station DCside array fault diagnosis method established based on the probabilistic neural network is high in diagnosis precision, and finally, branch current data are inputted to the photovoltaic array fault diagnosis model to realize diagnosis of multiple types of fault, and the existing data of the actual project can be fully utilized effectively.