Abstract: Generally speaking, the study of paleoenvironmental changes in southern Xinjiang is much more lackward because of the difficulty to obtain an ideal geological record which bears high resolution paleoclimatic information. Recently, a synthetic study on the stratigraphic and geochemical characteristics of the sediment since about 4 ka B.P. in Cele district, southern Xinjiang, has shown that during this period, although the dry state always existed, there were still several variations of relative wet periods and aggravated periods. Combining with the chronological and sedimentary studies, before about 2 000 a B.P., climate was dominated by relative wet, but after this time boundary, it was characterized by consecutive drought, and with four intense desertification periods being revealed, i.e. since about 1 500 a B.P., the climatic characteristics similar to modern climate of this area had basically appeared at about 1 200 a B.P. to 1 000 a B.P., 1 000 a B.P. to 630 a B.P.and after 200 a B.P.. In the aridest southern Xinjiang, natural environmental changes play very important role in affecting the man land relationship, especially in the early historic period. It is of interesting to compare the abandonment of ancient cities in southern Xinjiang with the climatic and environmental changes, for example, these above mentioned abrupt climatic dryness basically coincide well with the periods of intense abandonment of the ancient cities during early 5~6 century, the Song and Yuan dynasty, and the Ming and Qin dynasty respectively. So, in order to further realize the content of man land relationship and its development, we shall pay special attention to the time scales, because during different time scale, the affecting factors of man land relationship would have been changed, but it is undoubtedly, during late period of historic time, the influence of human being had been getting more evidently and importantly.

Key words: Tarim basin, climatic and environmental change, abandonment of ancient cities, since about 4 ka B.P.