Abstract: Based on sun's activity data, the effect of sunspot and El Niño event on the hydrologic regime and the flood and drought long-term fluctuation of the Songhua River region was analyzed by using statistical method for long-term prediction. The relationship between the El Nino event and 11-year period of sun's activity was revealed through dividing the sun's activity into a strong and a weak section during 1810-1991, a "same year" hydrologic compution formula with sunspot numbers as a parameter was proposed, the fluctuation of the flood and drought influenced by the events in the strong and weak sections was analyzed since 1899, and the periodic change of annual precipitation with the high and low water year was given according to the magnetic cycle.