The trend analysis is employed for the solar radiation reaching the surface from 1959 to 1993 in Hefei. The results show that the annual mean scattered, direct and global solar radiations decreased at a rate of 48MJ /m2·10a, 454Ml/m2· 10a and 29MJ/m2·10a respectively. The decreasing of solar radiation is closely related to the average growth rate of urban population.