Abstract: A day-to-day analysis of the distribution and disposition of the large-scale water vapor transportation and its variation over the low-latitude areas of both hemispheres was carried out by using FGGE-Ⅲ B data, part of OLR data and satellite cloud pictures from May to July of 1979. Vertically integrated (from ground level to about 300 mb) water vapor flux vector diagrams were utilized for the analysis in a visual way to show the characteristc features of the three-dimensional large-scale air flow. It was found that the large-scale transportation was characterized by spacial continuity, time stability and clear-cut structure.The evolution of intensity and mutual disposition of the large-scale water vapor transportation air currents from different sources during the seasonal transition of general circulation were described. It is considered a reflection of the interaction between the northern and southern hemispheres as well as between mid and low latitudes in the northern hemisphere in terms of water vapor transportation.Finally, several conclusions contributory on the synoptic meteorology were obtained,