Abstract: Based on the data of solar radiation measurement of 21 years, the Linke turbidity factor in Beijing district are analysed and its yearly changes and trends are discussed, too, in this paper. It shows that the average value of turbidity factor of 21 years is about 3.25 and Beijing tends to be in the rank of turbid cities. In the yearly changes of atmospheric turbidity factors, the largest turbidity value is in summer, about 3.67, in winter it is the smallest, about 2.89. There are three positive departure values of T in the changes year by year. In the end of 1950’s the positive departure had been affected by local environment of Beijing. In the middle period of 1960’s T increased because of Agung volcanic eruption. Since 1970’s the atmospheric turbidity have been increasing year by year, with the industrial development and the growth of population in Beijing.