Abstract: On the basis of ²¹⁰Pb dating, the variation of elemens was studied for the Ulansuhai Lake sediments. Using the cluster analysis method, the influence factors were also discussed. The results show that some elements, such as Ca, Sr, Cu, Mn, P and so on, declined with depth generally, but the remaining ones had an overall upward increasing trend. By the analysis of enrichment coefficient variations of the lake sediment elements, it was found that the enrichment coefficient of some elements, for example, Ca, Sr, Cu, Mn and P,have the same trend with their contents, suggesting that they was affected by the sediment input. The others, such as Al, K, Be, Ba, Mg, have different trend with their element contents, but were in line with the clay content.Heavy metals, such as Cr, Fe, Ni, V, Co, Pb, Zn, may be affected by clay adsorption. Finally, the ordered specimen cluster analysis method was applied to study the lake environmental changes. It was found that the distribution of sediment elements shows some kinds of environmental events in the process of lake evolution, such as the lake formation, the abrupt change in water quality in 1970s and the discharge of domestic sewage and industrial wastewater into the lake in recent years and so on.