[Objective]The research aimed to analyze and contrast flood cause in Nenjiang Basin between 2013 and 1998.[Method]Based on meteorological and hydrological data in and around Nenjiang Basin,geographic information system as data processing platform,statistical methods such as synthesis analysis and correlation analysis were combined to contrast and analyze the flood cause in the Nenjiang Basin between 2013 and1998.[Result]The similarities of two floods in Nenjiang Basin were that rainstorm frequency and summer precipitation were more,and many large and medium-sized reservoirs which undertook the flood control task were running above flood level.In order to protect the safety of reservoir dam,flood discharge volume increased.And the difference was external forcing factor which caused atmospheric circulation abnormality,thus the impact factors of summer more rainfall were not the same.The main reason for more precipitation in Nenjiang Basin in summer of 2013:The northeast cold vortex activity was frequent,and the path was by north;water vapor transport was sufficient at 850 hPa;at 500 hPa,the Eurasian zonal circulation was weak,the West Pacific subtropical high pressure abnormally moved northward,blocking high of the Sea of Okhotsk was obvious,and Heilongjiang region was controlled by negative anomaly in midsummer;East Asian westerly jet location was abnormal at 200 hPa,and East Asian summer monsoon was strong.[Conclusion]The research had very important significance for understanding occurrence rule of flood and improving disaster prevention and mitigation capabilities in Nenjiang Basin. [Objective] The research aimed to analyze and contrast flood cause in Nenjiang Basin between 2013 and 1998. [Method] Based on meteorological and hydrological data in and around Nenjiang Basin, geographic information system as data processing platform, statistical methods such as synthesis analysis and correlation analysis were combined to contrast and analyze the flood cause in the Nenjiang Basin between 2013 and 1998. [Result] The similarities of two floods in Nenjiang Basin were that rainstorm frequency and summer precipitation were more, and many large and medium-sized reservoirs which undertook the flood control task were running above flood level.In so to as to protect the safety of reservoir dam, flood discharge volume increased. And the difference was external forcing factor which caused anomalous circulation abnormality, thus the impact factors of summer more rainfall were not the same The main reason for more precipitation in Nenjiang Basin in summer of 2013: The northeast cold vortex activ was was was was and water water water water water water water , and Heilongjiang region was controlled by negative anomaly in midsummer; East Asian westerly jet location was abnormal at 200 hPa, and East Asian summer monsoon was strong. [Conclusion] The research had very important significance for understanding occurrence rule of flood and improving habit prevention and mitigation capabilities in Nenjiang Basin.