Based on the NCEP/NCAR reanalysis data from 1948 to 2009,this paper studies the spatial and temporal characteristics of vertically integrated water vapor content of annual average,January,April,July and October over the Yellow River basin.Results show that the annual average water vapor content is 5—27 mm.The water vapor content reaches the minimum in winter(January) and the maximum in summer(July),and it is the lowest over the Tibetan Plateau and the highest over the lower Yellow River,while it is in the middle over the westerly belt.By means of REOF(rotated empirical orthogonal function) method,the atmospheric precipitable water of annual average,January,April,July and October can be divided into two,four,four,four and four sub-regions over the Yellow River basin,respectively.The water vapor content over the whole basin and the middle and lower Yellow River basin tends to decrease,while the trends are different over other subareas.