Abstract: The summer monsoon brings plentiful water vapor, which is important for vegetation's growth andpeople's subsistence.T he relation between monsoon's northward advance and north boundary's locationis consanguineous.There are many monsoon indexes, and nor thward advancing of summer monsoon hasalso been investigated a lot.The research method considering vegetation growth angles proves to be accordant with the monsoon's influences on China. Station data and grid data including the daily rainfall dataof 715 stations of China from 1951 to 2006 are used to depict the summer monsoon's advancing process.Moisture transport is also investigated using NCEP/NCAR monthly mean and daily reanalysis data. First, the soaking rainfall index is defined to determine the East Asian summer monsoon area.It takes appearingsix times and more soaking rainfall (20 mm) processes during April to October as the standard, then theboundary belt positions for summer monsoon are defined according to the range of six times soaking rainfalllines waving variance annually, and wind vector changes in the boundary belt.Analyzing the continual soaking rainfall processes, the time when periods of drought ends is defined as the start time for summer monsoon in East Asian.This start time can represent the summer monsoon's northward advance.Besides, thecharacteristics of annual and decade variance of East Asian summer monsoon's north boundary and the variance of boundary belt's scopes are analyzed.Furthermore, the advanced process of East Asian summermonsoon's north boundary and its influence to the rainfall in China are investigated.To seek the cause about north boundary for summer monsoon waving unconventionally, it is important to analyze moisturetransport which maybe one important gene.The results show that : the soaking rainfall standard ascertainsboundary belt location for East Asian summer monsoon preferably, and it appears a tendency of southwardmoving and the scopes of boundary belt are enlarged.In brief, the location variance of East Asian summermonsoon's north boundary have a close correlation with south wind strength and moisture transport.It also has a certain influence to the rain band distribution of China as well as the precipitation in north of China, north boundary inclined north, also does the rain band, and the rainfall is relatively more in the northof China.