Based on the solar radiation information and climatic observation data from 1961 to 2011 in both East and West China, the interannual trends of surface solar radiation are investigated. By combining with cloud cover, sunshine percentage, sunshine duration, wind speed, atmospheric turbidity, and relative humidity, the causes affecting the variations of the total surface solar radiation in East China and West China are analyzed. The results show that the surface solar radiation decreased from 1961 to 2010 in both East and West China, but there was an abrupt change, which occurred in the early 1990s, followed by sustained increase. The surface solar radiation decreased from 1961 to 2010 in East China, and the decrease of surface solar radiation in the eastern region was greater than in the western region. The surface solar radiation is significantly correlated with sunshine duration in both East and West China. In East China, the surface solar radiation is significantly positively correlated with the percentage of sunshine. It indicates that the percentage of sunshine duration is the main factor affecting the total surface solar radiation in East China. The decrease of the total surface solar radiation is influenced by many factors. In East China, the percentage of sunshine and the atmospheric turbidity factor are the main factors affecting the surface solar radiation reduction. There is no correlation between cloud and ground solar total radiation. However, the percentage of sunshine is affected mainly by cloud cover and air pollution. In West China, no significant correlation is found between surface solar radiation and cloud cover, but significant correlation is detected between surface solar radiation and sunshine percentage. These indicate that the sunshine percentage could be a main factor affecting surface solar radiation. Wind becomes an important factor affecting the total surface solar radiation, since wind is a main factor expelling troposphere air pollution such as smog. A comparison of the variation in ground solar radiation between the East and West China shows that the aerosol particles of air pollution are the main factor affecting the reduction of total surface solar radiation in East China. Many scholars have found that the significant reduction of the surface solar radiation is mainly due to the absorption and scattering atmospheric aerosols. All these findings suggest that the air pollution has become an important factor affecting the surface solar total radiation, especially in East China.