Abstract: Abstract.By analysing the causes of the great flood of 1931 and the severe drought of 1934 the author found that (1) the number of continental shallow depreessions,(2) the intensity of the Japanese high pressure and the time of its southward migration and (3) the intensity of the Pacific high pressure were closely related with the flood and the drought.The greater number of shallow depressions in the summer of 1931 and a well developed high pressure over the sea of Japan blocking the tracks of these depressions were directly responsible for the disaslrous flood in the Yangtze valley.On the other hand the drought of 1934 was the result of the interaction of the following causes:(1) too few cyclones in the summer,(2) a weak Japanese high pressure and its too early arrival in the sea of Japan and(3)a strong Pacific high pressre.