The monsoon transitional zone (MTZ)in East Asia，located near the north fringe of East Asian summer monsoon (EASM)，is characterized by fragile ecosystem and climate sensitivity． The precipitation over the MTZ is not only significantly linked to variations of EASM，but also closely associated with the mid-and high-latitude westerlies． The precipitation variations over the MTZ in East Asia differ from those in classical monsoon region and arid region and are currently not fully investigated． Focused on the characteristics and physical mechanisms，this paper reviews the factors for the interannual variations of summer precipitation over the MTZ in East Asia such as sea surface temperature anomaly in tropical key areas and extratropical atmospheric teleconnections，etc．，and the potential impact of Pacific decadal oscillation (PDO )，Atlantic multidecadal oscillation (AMO )，and external forcings on interdecadal variations of precipitation over the MTZ． Based on the progress of the previous studies，we put forward several related issues that need to be further investigated in future，for instance， quantitatively distinguishing the relative contributions of external forcings and internal variabilities to the interdecadal variations of precipitation over the MTZ．