Dust deposition on photovoltaic (PV) modules seriously affects the stability of PV system output, resulting in the reduction of generated power and shortening the service life of the PV modules. The accurate assessment of dust accumulation concentration in the PV field will help to improve the accuracy of the power prediction model of PV power generation. In this paper, the dust particles collected in PV power station are taken as the research object. Firstly, the elemental composition, content, morphological characteristic and particle diameter distribution of the dust particles are analyzed. According to the actual power generation efficiency of PV modules and environment parameters, a soft measurement model of dust accumulation concentration is established to rapidly evaluate dust accumulation degree of PV power station. Secondly, in order to accurately obtain the relevant parameters of the model, several experiments on the influence of dust accumulation concentration on power generation performance are carried out to obtain the relationship between the output power of PV modules and irradiance, dust accumulation concentration, as well as module temperature. Finally, the accuracy and reliability of the model are verified in natural conditions. The results show that compared with other traditional methods the proposed model has better prediction performance, and the accuracy can reach 89. 6% .