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Using the drought/flood data from representative stations over the eastern Northwest China from 1470 to 2003 collected by the Chinese Academy of Meteorological Sciences, according to different features of terrain, physiognomy and climate, the eastern Northwest China is divided into three climatic regions. By means of statistic methods such as periodic analysis and coil3 wavelet transform, an analysis is made of the decadal variation of drought/flood index in three climatic regions and the difference among them. Results indicate that the spatial and temporal distribution features of drought/flood in three regions are different, and the variation trend and periods not only show consistency, but also exist obvious difference. The drought climate tended gradually to be normal or became wet in the north and the central parts of the area in past 534 years. From 1470 to 1724, the drought climate in the south part tended to be wet. However, after 1724, the wet climate became dry again. There are notable periods of 25 and 10 years in drought/flood in the three regions, respectively. In addition, there are obvious periods of 14 to 15 years in the central part. It is illustrated that the alternation of droughts and floodd is more distinct in the central part than those in the north and south parts.