Abstract: The maximum precipitation in the Yangtze River Delta which were caused by the tropical cyclones landing in the South China Sea in 1949—2000 were studied. The probability of precipitations above 50 mm was worked out when there was a tropical cyclone in the South China Sea. It is about 60 percents. A wavelet transform about the frequency of the tropical cyclones was performed. The results show that this series has notable oscillations and the periods vary in some regulations. As results of a cross power spectral analysis about the frequency series of the tropical cyclones and the sum series of the subtropical high area indexes of July, August and September, the two series have quasi-two-year and quasi-five-year coupled oscillations. The anomalies in the West Pacific, the Atlantic and the North Pole were found out when the Northern Hemisphere 500 hPa height data of anomalistic years were analyzed.