The characteristics of summer water vapor transfer are studied by using the NCEP/NCAR reanalysis data from 1958 to 1998. The results show that the zonal vapor transfer is from west to east in middle-high latitudes and from east to west in low latitudes in the both hemispheres.The meridional vapor transfer is from the southern hemisphere to the northern hemisphere in summer and vice versa in winter. The net vapor transfer is also from the southern hemisphere to the northern hemisphere for annual average.Subtropical areas in the both hemispheres are the sources of water vapor, and the eqautor and middle-high latitudes are the sinks. The three rain-bands over China in summer correspond to three different types of the convergence of anomalous water vapor transfer.