In order to explore the potential transmission capacity and overcome the defect that solar radiation intensity is regarded as a constant when the transmission capacity of overhead conductors is calculated,by adopting a solar radiation intensity gradient of 100W/m²,the influence of the solar radiation intensity on the transmission capacity of overhead conductors of different kinds of cross-sectional areas is discussed.Then,on the basis of the atmospheric attenuation law of solar radiation and by introducing an attenuation coefficient,a real-time solar radiation evaluation model is constructed.In the model,according to specific time and the longitudes and latitudes of different regions,the problem is converted into another problem of calculating the distance of the solar radiation getting through the atmosphere,thus realizing the purpose of evaluating the real-time solar radiation intensity of a region.Finally,by using the meteorological data of Datong,Shanxi Province in 2012 and the data calculated by the formulas of IEEE 738—2006,the accuracy of the constructed model is verified.It is found that the data calculated by this model can fit the meteorological data well,with a maximum error within 70W/m²,and the fit is better than the data calculated by the formulas of IEEE 738—2006,which means that this model can meet the requirements of calculating the transmission capacity of overhead conductors.