Abstract: Based on NCEP/NCAR, the ERA-40 reanalysis dataset, and the precipitation dataset from 753 stations in China, the interdecadal variation of the summer Pacific-Japan (P-J) teleconnection pattern is investigated. Results indicate that the summer P-J teleconnection pattern experienced a marked interdacadal variation around the late 1970s, with its major teleconnection centers shifting southwestward. This interdecadal variation is clearly reflected in the fields of 850 hPa zonal wind and 500 hPa geopotential heights. This study also shows that the P-J teleconnection pattern in interdecadal variation is closely related to interdecadal variations in sea surface temperature (SST) over the tropical Pacific and Indian Oceans. Prior to the late 1970s, no high correlation coefficients are found between the summer P-J teleconnection pattern and its previous winter SST. However, after that, the P-J teleconnection pattern is found to be highly correlated to the SST over the tropical Pacific and Indian Oceans, both in the previous winter and spring. This interdecadal change in the relationship between the P-J teleconnection pattern and the SSTs over the tropical Pacific and Indian Ocean is probably due to the fact that the SST interannual variability over the tropical central and eastern Pacific has increased remarkably since the late 1970s. A high-resolution atmospheric general circulation model (GCM) is used to examine the effect of SSTs over the tropical Pacific and Indian Oceans on the interdecadal variation in the P-J teleconnection pattern through a model control experiment and several sensitivity experiments. GCM results further confirm that the interdecadal variation in SSTs over the tropical Pacific and Indian Oceans can indeed lead to the interdecadal variability of the P-J teleconnection pattern.