Sediment samples were collected from 126 sites in the Dianchi Lake and tested for concentrations for copper, zinc, lead, cadmium, chromium, mercury, and arsenic in different layers (0~5 cm, 5~10 cm and 10~20 cm). It was found that concentrations of these metals in these samples were much higher than their respective references, indicating that the sediments of Dianchi were polluted to a varying degree. metal concentrations in the sediment did vary significantly with depth and sampling site. Concentrations of Zn, Pb, Cd, Hg, and As were generally high in the upper layer except for Cu and Cr, which might suggest that the pollution of Zn, Pb, Cd, Hg, and As is getting more and more severe, while the pollution of Cu and Cr is put under control. With the Håkånson potential ecological risk index approach, ecological risk of the heavy metal pollution of the sediment in Dianchi Lake was analyzed. Results showed that the pollution of Cu, Zn, Pb, Cr, and As did not pose much ecological risk to the Dianchi Lake, while that of Cd and Hg did a moderate ecological risk. On the whole, the sediment in the Dianchi Lake was moderately polluted with heavy metals with a potential ecological risk index RI being 205.03, which was though moderate, but displays a trend of speeding up towards gravity.