Abstract: Self- Organizing Map is a method of artificial neural network , whichimplements patternrecognitionand data clustering simultaneously . SOMis able to convert complex nonlinear statistical relationships of high- dimensional datainto simple geometric relationships . Inthis article , we investigate the variationpatterns of precipitationintensity and maximumwater level in Poyang Lake valley withself-organizing map . Thenthe cause of flood disaster is discussed according to the result of calculation.