Using the datasets from 30 observational stations over mainland China, the authors studied the changes in annual and seasonal amounts of surface solar radiation from 1961 to 2003 and the spatial characteristics. Cause of the changes was discussed. The results indicated that surface solar radiation in mainland China decreased by approximately 11% from the early 1960s to the late 1980s in general, but increased slightly during 1990-2003. Nevertheless, the mean value of surface solar radiation over 1990-2003 was 8.2% lower than that over 1961-1965. Significant decrease occurred in the period from March to August, accounting for 55%-85% of the annual reduction. Analysis of the datasets for each station suggested that the trend in changes of surface solar radiation with time could be roughly identified as four groups with the characteristics of decreasing continuously (6 out of 30 stations) or leveling off (7 out of 30 stations) over the period from 1961 to 2003, and decreasing significantly from the early 1960s to the mid 1980s and leveling off thereafter (12 out of 30 stations) or increasing gradually thereafter (5 out of 30 stations). The four groups have no significant regional feature in spatial distribution. A main cause of the reduction in solar radiation is the decreasing sunshine duration. Approximately 72% of the variability in the solar radiation can be expressed by the sunshine duration which is positively correlated with wind speed.