The mean annual temperature in the thermal maximum of Holocene in the South China was about 1 ～ 2℃ higher than that of the present day. Many investigations showed that a distinct climatic change occurred in coastal areas of the South China at 4 ～ 3kaB.P. The distinct character of this change are the decrease in temperature, increase in seasonality and stronger rainstorm in summer. Comparing with the high resolution result from the Cariaco Basin in northern Venezuela, the simultaneity of the climatic change in the two opposite tropical coasts of the Pacific Ocean indicates that the this event might be related to the increase in ENSO variability. The present paper analysed additionally the human impact on vegetation since the Neolithic age, discussed the rise and fall of the fishing-hunting culture and probed into the history of agricultural development and the disturbance of ecosystem.