In order to find out the change point of water level in Poyang Lake， the annual mean water level and monthly mean water level of Xingzistation were diagnosed by comprehensive mutation diagnosis system. Sliding T test， Yamamoto method， Pettitt method and other seven kinds ofclassical diagnostic methods were applied to water level sequence， and a variety of test results confirmed each other to avoid the wrong conclusion.The results show that the change -points of the tested water level were concentrated in 1999 -2004， among which the most significantchange-point was in 2003. The annual average water level was decreased by 1.12 m. The results can provide guidance for the analysis of hydrologicalsituation and water resources utilization in Poyang Lake basin.