Abstract: Synthesizing the available data at home and abroad, the authors concluded that the global climate change controlls the desertification and de-desertification by its effect on the variation in dry-wet climate over sand area; on the other hand, the desertification and de-desertification have a feedback effect on global climate change in the way of its impact on the radiation equilibrium, condensation nucleus, moisture and convection. If the global climate became warming due to the man-made CO2 and other greenhouse effect gases, the developing tendencies of desertification in northern China sand area would be that when the precipitation in the eastern China sand area increased, the desertification process would be retarded, even reversed; and the precipitation in western China decreased, the desertification would be accelerated.Today's climate is substantially a result of coupling anthropogenic and natural climate. In the geological time, the recent stage and the future, natural climate must be a dominant part of the climatic factors and less of anthropogenic factors. The natural climate always fluctuates in diffierent periods and amplitudes, while the anthropogenic climate characterized by greenhouse effect of man-made CO2 and other trace gases would be linearly or exponentially varied. So the coupling of two parts——climate regime （such as temperature） occurred in a given time will have three potential situations rather than one: when natural change corresponds to the anthropogenic, the temperature will rise greatly; if the natural change is contrary to the anthropogenic and the former amplitude is greater than the latter, the temperature will drop, but slightly; if the natural change opposes the anthropogenic and the former amplitude is equal to the latter, the temperature will remain the same. Since the tendencies of natural change are uncertain so far, it is impossible to determine the trends of global climate change due to increasing anthropogenic greenhouse effect. The authors proposed that we must strengthen the study of natural climate change in the research of CO2 greenhouse effect.