Abstract:This paper analyze mainly the relation between northern pacific SSTA and east Asian summer monsoon, it is pointed that their interaction has feature of change decadely. Before 1976 the northern Pacific SST anomalies act on the east Asian summer monsoon by a great circle wavetrain, which causes northern-China precipitation abundance. After 1976 the northern Pacific SST animalies make the wavetrain weak, relation to East Asian summer monsoon will be weak. It shows that the key region that affect east Asian summer monsoon is not changeless, it will divert from one area to another.