Abstract: By use of 45-station rainfall from the Song hua jiang, Nenjiang and Liaohe (SN L)river v alleys and NCEP/NCAR reanalysis, study is made of the climate features of the summer basin rainfall over the valley s and the forerunner relative to the anomaly, proposing a qualitative prediction scheme for a flood or drought trend based on the Northern Hemisphere circulation anomaly in the previous November and December.The scheme introduces two indices for the anomaly of extratropical circulations, with which to satisfactorily discern and predict the singularities of the basin precipitation in summer.