Abstract: The wetness data at 100 stations were carefully examined by means of spectrum analysis. A pronounced spectral peak in the 36-yr. was observed in the data for Shanghai and the adjacent region. The geographical distribution of relative spectral power for sea-level pressure at different grid points in Northern and Southern Hemispheres showed a stronger peak in 36-yr. at central Pacific Ocean. This 36-yr. peak for general circulation was found to be closely related with the wetness of China. The South Oscillation's index were obtained from pressure differences between grid points 160°W', 10°N and 140°E, 20°S. A clearly 36-yr. oscillation was also revealed in the long-period variation of S.O. index. The mechanism of the 36-yr. oscillation was discussed.