The southeastern Tibetan Plateau has one of largest subtropical snow cover due to its low temperature and high precipitation. Changes of the snow cover in the southeastern Tibetan Plateau are not only influenced by the Asian summer monsoon but can also strongly feedback the dynamics of the monsoon by changing the thermal conditions of the plateau. The brevity of the instrumental snow cover data of a few decades has limited our ability to detect the interactions between snow cover and Asian summer monsoon, particularly for the interdecadal scale. This is a first tree-ring based snow cover reconstruction for the Tibetan Plateau. We collected 25 tree-ring chronologies in the southeastern Tibetan Plateau (28°~32°N, 92° ~ 98°E) and found 9 of them are significantly correlated with the snow cover changes. These 9 chronologies concentrate in northern Yunnan Province in the rain shadow region of the mountain ranges between Myanmar and China. Tree rings in these relatively dry regions are generally sensitive to moisture. Further, we found that the good matches between snow cover and tree-ring variations are only for the interdecadal changes but not conspicuous for the interannual changes. The interdecadal variations of these tree-ring chronologies agree with each other well through their common period of the past 300 years. This suggests that these chronologies are likely controlled by one environmental factor of the snow cover,and the relationships between tree growth and snow cover at the interdecadal time scale are stable over time. The snow cover modulates the growth of tree rings via modulating the soil moisture as indicated by the high correlations between tree growth and the snow cover and the drought index. The influences of snow cover on tree growth outcompete the other factors at the interdecadal scale, while at the interannual scale, tree growth may be dominated by the local climate change as indicated by varying interannual variations among these 9 tree-ring chronologies with coherent interdecadal variations. Our study adds in evidences that different environmental factors may modulate tree growth at different time scales. This study reconstructed the snow cover changes in the southeastern Tibetan Plateau over the past 300 years using tree rings and explored its linkages with the Asian summer monsoon. The tree-ring based snow cover reconstructions agree well with the drought reconstructions from the local historical documets.