Abstract: The relationship among solar activity,the sea temperature in the Kuroshio region and the flood and drought in the Middle Reach of the Yangtze River (MRYR)is investigated by using 30 years'data of solar activity,the sea temperature in the Kuroshio region and the rainfall in the MRYR. Results show that the rainfall in the MRYRis obviously controlled by the interannual and seasonal variations of solar activity and the sea temperature in the Kuroshio region.The solar 10.7cm radiation flux is taken as the index of solar activity and the interannual fluctuation curve of the difference of F_10.7 between winter and summer oscillates with a period of about 11 years.The flood years(or drought years)frequently occurred when the positive part (or negative part and odd point) of the curve appeared 3 years ago and the last year lay in the peak (or valley,or near zero point)of the seasonal variation curve of the sea temperature in the Kuroshio region.According to these features, the solar activity data in the previous two years and the sea temperature data in the Kuroshio region before this spring can be used to analyze the trend of flood or drought in the MRYRin the coming summer.