Based on the radiation data from May of 2009 to April of 2010 at Yangbajing in Tibet,the daily,monthly and seasonal variations of total radiation,ultraviolet radiation,long-wave radiation and net radiation were discussed and the frequency and reasons why the radiation exceeds the solar constant were analyzed.The results show that the total radiation,ultraviolet radiation,long-wave radiation and net radiation in Yangbajing area present obvious daily,monthly and seasonal variation characteristics.There is a positive correlation between the total radiation and ultraviolet radiation,between the total radiation and short-wave reflected radiation over earth surface and between the downward atmospheric radiation and long-wave reflected radiation over earth surface.