Abstract: Storms of the Bay of Bengal have an important impact on southwest water vapor transportation, with double-peak periods (May and Oct-Nov) occurring in storm active stage. According to 2001-2010 JTWC (Joint Typhoon Warning Centre) storm data and NCEP (National Centers for Environmental Prediction)/NCAR (National Center for Atmospheric Research) 1°×1° reanalysis data on southwest water vapor transportation in double-peak periods, the storm water vapor is transported most strongly northward, followed by eastward transportation. Transportation in other directions is weaker. In the center and southwestern areas of the storm, each layer of water flux and all layers combined are higher than the climate average value for the southwest. In the double-peak periods, storm meridional moisture transportation is double than that of zonal transport. The actual southwest water vapor transportation for storms in May is twice as large as that in Oct-Nov. The effect of water vapor transport prior to the peak period (May) for storms in the Bay of Bengal is greater than that after the peak period (Oct-Nov). the Bay of Bengal storms are therefore one of the main systems for southwest water vapor transportation in May.