Abstract: Drought and flood disaster is one of the most natural disasters in China, and it posed serious threat to the life and wealth of people, and the social sustainable development. Therefore, there is an important implication for the scientific research of the drought and flood disaster. To the drought and flood disaster itself, although its occurrence with sudden, it is still a certain regularity with a number of data and research results. Therefore, there are many important methods of the research of the drought and flood by the analysis of historical data，among of them, reconstruction analysis for long time series which is a comparable efficient method to research the drought and flood disaster can find the regulation of development of the drought and flood disaster. Recently, some scientist had researched the Jing River, Malian River, Fen River, and Urumqi River with the reconstruction analysis for long time series, and gained lots of success. However, there have been no people researched and analyzed the Qianhe basin which is the branch of the Wei River. Collecting and classifying the data about drought and flood disasters in Qianhe basin from 1470 to 2009, and using methods of moving average, accumulative anomaly and wavelet analysis, the change law of drought and flood disasters in the recent 540 years was analyzed, the results showed that the drought and flood disaster happened frequently in the Qianhe basin from 1470 to 2009, and had obvious features of phasic rule and periodic law, which was close correlation with the the drought and flood disaster in the northwest of China, especially Guanzhong plain. The study was very important to realize change law and draw prevention measures of drought and flood disaster in Qianhe basin. According to the results of 11years moving average and accumulative anomaly, it is concluded that the drought and flood disaster of Qianhe basin could be divided into three stages. From 1470 to 1640, the drought and the flood disaster were both seriously; from 1640 to 1880, they were comparable balance; from 1880 to 2009, the flood took place frequently. At the basis of three stages, we could further divide them into seven droughtpartial or floodpartial periods. In addition, by wavelet analysis, it was found that the 540 years’ drought and flood disaster of Qianhe basin changed obviously in law, and associated with the action of the sun closely. And the drought and flood disaster for the Qianhe basin had obvious relevance in Northwest China, especially in drought and flood disasters in the Guanzhong area. The all results of the research have important practical significance for the development of disaster prevention and mitigation measures of the Qianhe basin.

Key words: Qianhe Basin, drought and flood disasters, change law