Abstract: Based on the monthly precipitation of 13 stations in the Tarim River Basin between Apri1 and September from 1961 to 2001,the mann-Kendall method was used to test the abrupt change of precipitation,the Z index,the Maximum entropy transformation and climatic tendency coefficient were used to calculate the grads,cycle and tendency of drought-flood.The results show:(1)the precipitation of source area,upper,middle and lower reaches increased in different periods,and the abrupt changes occurred in the every increase process,the abrupt change time is more and more earlier from source area to the lower reaches,the time was in 1990,1975,1973 and 1969.(2)The drought was frequent and serious in the 1960s,the times of drought decreased and times of flood increased from the 1970s to the middle of the 1980s,while these droughts and floods were serious.The times of drought decreased obviously while the times of flood was dominant from the later period of the 1980s to earlier period of the 1990s,the flood was dominant and most serious,while drought was less and light.Since the middle of the 1990s,the increase of flood was main in source area,upper reaches and middle reaches,but the flood was becoming light in these areas,while the variation of lower reaches was different from the others,its times of flood decreased,while its times of drought increased and drought was becoming serious.(3)The cycles of drought-flood are 2.5 years and 13.3 years in source area,40 years,6.7 years and 2.5 years in the upper reaches,10 and 2.7 years in the middle reaches,2.4 years,6.7 years and 3.3 years in the lower reaches.The tendency of drought-flood was becoming wet,the test show that the tendency was prominent in the upper reaches,faint in the lower reaches and not obvious in the middle reaches.(4)The NAO′s impact on drought-flood is remarkable in the upper reaches and the middle reaches.