Abstract: Basing on the system theory and making use of the system methods,this paper studies and analyses the process of formation and development of desertification.In fact,desertification is the degenerating process of geographical environment of arid,semi-arid and semi-humid reg ions.Due to the incoordinating interaction of two inner factors of man-nature system-natural environment and mankind activity,the system deviates from its balance state and the balance can not be rehabilitated by its inner self-organization and feedback mechanism.Finally,all these result in the degeneration of natural elements of man-natural system.Then,the desert landscape takes the place of the sparse woodland rang eland landscape.So we can say that the whole development process of desertification is also an evolution process of man-nature system's structure and function.In the process,the inner elements and outer environments take place the change through the fluxes of energy,matter and information.From the above,we come to the conclusion that the key of resolving desertification of arid regions and achieving regional sustainable development is that mankind should develop social economy and raise productivity firstly,then in the guide of rational social institution,economy policy and progressive productive methods,bring into play the subjective activity,harmonize the relation of man and nature of arid regions,adjust the structure of key elements of man-nature system,keep the stability of the system.

Key words: man-nature system, desertification, sustainable development