Abstract: Taking the surface dirt of PV modules as the research object,nano cleaning agents are used to clean the surface dirt of PV modules,and then nano coatings are coated on the surface of PV modules to study the effect of dust and other dirt on the power generation efficiency of nano coated PV modules. This paper takes an actual PV power station as an example to conduct a comparative experiment of three groups of PV strings,including cleaning and coating treatment,only cleaning treatment,and no treatment. The single watt power generation of PV strings is collected as the basic data during the annual testing period,and the difference in power generation efficiency and energy efficiency improvement rate of PV strings are calculated. The experimental results show that during the testing time,the average difference in power generation efficiency of the PV string treated with cleaning and coating is 7.6% higher than that of the PV string treated only with cleaning. And the nano coated PV modules are suitable for PV power stations in rainy and humid areas. The faster the surface area of the PV modules is cleaned,the faster the cost recovery.