Heavy metal concentrations (As, Co, Cr, Cu, Hg, Mn, Ni, Pb, Zn) of superficial sediments in the Nansihu Lake were investigated in April, 2002. The determination of the heavy metal distribution of the lake's superficial sediments was carried out by ICP-AES. The potential ecological risk index (RI) and geological acumination index(I_geo), as the quantitative diagnostic tools, were used to evaluate the pollution degree of various heavy metals in the sediments. The results show the distribution of pollutants in the sediments could be divided into three sections with different ecological risk characteristics:(1) light pollution area in Zhaoyang Lake, (2) medium pollution area in Dushan Lake, and ⑶ heavy pollution area in Nanyang Lake.