Abstract: Characteristics of the climatological mean summertime water vapor transports for 1971-2000 over the monsoon region of eastern China and those over the arid and semi-arid regions of Northeast China and their differences are analyzed by using the daily data of the ERA-40 reanalysis. The results show that there are some obvious differences between the summertime water vapor transports over the monsoon region of East China and those over the arid and semi-arid regions of Northwest China. Since a large amount of water vapor is transported by the Asian summer monsoon flow from the Bay of Bengal, the South China Sea, and the tropical western Pacific into the monsoon region of eastern China, the meridional water vapor transport fluxes are larger than the zonal water vapor transport fluxes in the monsoon region of eastern China in summer. But influenced by the westerly zone over mid-latitudes, the summertime zonal water vapor transport fluxes are larger than the meridional water vapor transport fluxes in the arid and semi-arid regions of Northwest China, and either zonal or meridional water vapor transport fluxes in the region are one order of magnitude smaller than those in the monsoon region of East China. Moreover, the results show that the divergence of the summertime water vapor transport fluxes in the monsoon region of East China depends on not only the moisture advection, but also the convergence or divergence of wind field over this region, but it mainly depends on the moisture advection in the arid and semi-arid regions of Northwest China. Besides, the results also show that the water balance in the monsoon region of eastern China is obviously different from that in the arid and semi-arid regions of Northwest China. 