The invention relates to a distributed photovoltaic system efficiency evaluation method and device based on cloud data analysis. The method comprises the steps: establishing a comprehensive evaluationindex system with the natural resource index, the electric quantity, the energy consumption, the equipment operation level and the economic benefit as the indexes and calculating the indexes; obtaining the index data to form an evaluation judgment matrix; determining the index weight by using the comprehensive objective weight method; and calculating the evaluation value of the photovoltaic powerstation operation characteristics according to the weight and performing performance analysis of the photovoltaic system through comprehensive evaluation of the single index and multiple indexes fromdifferent time scales and spatial scales. The device comprises an index calculation module, a standardized processing module, an objective weight calculation module and an evaluation value calculation module. The evaluation result can be used for analyzing the potential safety hazards of photovoltaic modules and other components as well as the actual impact on power generation of the power station and giving suggestions to improve the efficiency of photovoltaic power generation.