Using the NCEP/NCAR daily and monthly reanalysis data from 1948 to 2002,the climatic distribution of heat source over the Tibetan Plateau in spring,the interdecadal variation of the heat source over the eastern Tibetan Plateau,and the relationship of its anomaly to the East Asian summer monsoon are analyzed.The results show that there was an abrupt change in the spring atmospheric appearent heat source over the eastern Tibetan Plateau in 1965,and especially,the increasing trend of the heat source was remarkable after 1970.Furthermore there was an interdecadal relationship between the spring heat source over the eastern Tibetan Plateau and the East Asian summer monsoon.That is to say,there exited a negative correlation between them before 1978,but the relationship has become blurred after 1977.