Sediment samples collected at 126 sites in Lake Dianchi were analyzed to determine their metal concentrations of copper, zinc, lead, cadmium, chromium, mercury, and arsenic at different depths of the sediment cores (0-5cm, 5-10cm and 10-20cm). Based upon the consensus-based sediment quality guidelines (CBSQGs), the threshold effect concentration (TEC) and the probable effect concentration (PEC), five sedimentary environment quality grades were classified and assessed by employing the method of the grey clustering analysis. Results showed that sedimentary environment quality in Lake Dianchi is mostly in the third grade (III) with a moderate metal contamination. Sediments are the third grade (III) at the depths of 0-5cm and 5-10cm, and the second grade (II) at the depth of 10-20cm. Generally, sedimentary environment qualities in the deeper layers are better than in the upper layers, indicating that metal contamination in Lake Dianchi sediments trends towards worse.