Abstract: In this paper, the equatorial westerlies (E/W) and tropical disturbances (T/D) over the South China Sea are investigated for June-September, 1973-1984. The result shows that E/ W contributes to some extent to the generation and development of T/D, the latter, in return, further enhances the south E/W of T/D,which tends to cause T/D to change its direction of motion. There is a transfer of energy in this process of interaction. Referring to the equations of horizontal motion and vorticity, the variability of E/W is derived, and they indicate a major dependence of the local change in E/W upon the transportation of general amount of energy and vorticity. It is also found that there is a leading correlation between the variability and value for E/W, by which estimates can be made for the evolving tendency of the equatorial westerlies and tropical disturbances.