| Lake Chaohu, which is located in the areas along the middle and lower reaches of the Yangtze River of China, is considered as the study object. Cored CH-1 in the central of the lake, with gained sediment samples, based on informations from testing and calculating sediment grain size,magnetic characteristics and natural elements, as well as sediment chronology, this study rebuilds the environmental evolution during nearly the past 800 years in the watershed of Lake Chaohu. Further more, 14 tested indicators such as clay content,magnetic susceptibility,SIRM and so on are selected to execute principal component analysis, then fix 11 new integrated indicators to run cluster analysis, and finally this study creates the environmental evolution sequence about the past 800 years. Based on researches above, the main conclusions are as follows:1.Based on the sample dating results of 210Pb from Core CH-1 in central Lake Chaohu, its average deposit rate is about 0.17cm/a, so the whole core CH-1 covers approximately 800 years since AD 1 177.2.Sediment from CH-1 is mainly consisted of fine silt, which takes over a half, medium silt and clay next, the least is sand content; while magnetic minerals are mainly absorbed by clay, and them are mainly consisted of ferromagnetic minerals. Overall, core CH-1 locates in the central lake, where has a stable deposit condition with a weak hydrodynamic environment, so river function has faint affection on the sediment, and finally lead to fine grain size. Generally, the clay content is higher, the magnetic susceptibility is higher relatively, and the magnetic mineral grain is coarser; on the contrary, the clay content is lower, relatively, the magnetic susceptibility is lower, while the magnetic mineral grain is finer. Considering the vertical variations of the sediment grain size and magnetic characteristics, core CH-1 was divided into 4 sedimentary chronological sections.①1 177aA.D.～1 271aA.D.(Corresponding to 141～125cm)is proven to be a wet period according to both grain size and magnetic characteristics, which matches along with the Medieval Warm Period(MWP).②1 177aA.D.～1 271aA.D(.Corresponding to 125～44cm)is proven to be a wet/dry period, the frequent wet/dry alternative action causes the inconsistency of indications resulted from grain size and magnetic characteristics. There are 5 extreme drought events totally and the most drought event is in 1 747aA.D. or so at the end of this period. Actually the weather was dry and cold overall, which indicates the climatic characteristics of The Little Ice Age(LIA)in Eastern China.③1 747aA.D.～1 865aA.D.(Corresponding to 44～24cm)is considered as a continuous warming period after The Little Ice Age Maximum, during which had low precipitation. There was an important environmental change event in 1 747aA.D. or so, and this time could be an important boundary of Lake Chaohu environmental evolution history.④1 865aA.D. to Present(Corresponding to 44 to the top)is considered to be a continuous colding and drying process, whose maximum happened in 1 935aA.D., based on both grain size and magnetic characteristics changes.3.Neutral elements TOC,TN,TP content variations of core CH-1 show evident correlations with the clay content, the correlation index are all above 0.7, indicates those neutral elements are absorbed in finer sediments. Unlike the indications based on the grain size and magnetic characteristics, it could be divided into 3 stages between 1 271aA.D. and 1 747aA.D..①1 271aA.D.～1 477aA.D.(Corresponding to 125～90cm): During this period, the organic matters mainly came from water plants in Lake Chaohu, all the 3 neutral elements values were under a low value stably and fluctuating within a narrow range, but generally declined.②1 477aA.D.～1653aA.D(.Corresponding to 90～60cm): During this period both TOC and TN ascend while TP declines in a small trend; the sediment organic matters accumulated considerable high and the lake sediment experienced an affected process by the land-derived matter. Due to the maximum affections of the land, 3 neutral elements contents come to their maximum such as TOC,TN, especially ,the value of C/N reached to its largest value of the whole core, which indicates that the accumulation of TOC generally came from the organic matter of land plants.③1 653aA.D.～1 747aA.D.(corresponding to 60～44cm): TOC,TN,TP contents, as well as C/N ratio, declines after 1 653aA.D. , by which time they reached their peak values. Neutral elements valley values such as TOC,TN,TP appeared at 47cm,44cm,49cm in sequence, it shows that the organic matter accumulation low. This conclusion is consistency to the extreme cold event in 1 747A.D. reflected by the sediment grain size and magnetic characteristics at 44cm. During this period TP average content was 0.044, which is much larger than the average content between 1 477aA.D. and 1 653aA.D. , it merely was 0.027. Sediment TP content increased substantially because of the fast increasing population and growing farmland, in addition to the profound knowledge of the fertilizer on farming.4.Following principal component analysis on selected 16 typical indicators by running SPSS15.0, such as clay content,χ,SIRM and so on, 11 target variables that can closely reflect the information of environmental evolution are confirmed, then, cluster analysis of the total 113 cored samples is conducted based on this result. It is showed that the total samples from core CH-1 in Lake Chaohu could be divided into 4 classes and 2 subclasses. Following the classified classes, environmental evolution sequence of Lake Chaohu area for the past approximate 800 years had been rebuilt. Finally, based on those analyses above, environmental evolution integrative sequence in Chaohu district is reconstructed.
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