Abstract: Different fractions of arsenic of surface sediments taken from Lake Chaohu were studied using BCR sequential extraction procedure, and the pollution level of Arsenic was evaluated. The results indicated that the total content of arsenic was higher than the background value obtained from the statistics of 663 sediment samples in 9 lakes in a regional eco-geochemical survey. The pollution mostly existed in the east and west part of the lake while lower content in the middle part. It was found that Arsenic was distributed mainly in residual fraction, being attributed to 68.64%-79.24% of total arsenic. The contents of soluble fraction, reducible fraction and oxidisable fraction were 1.18-2.82, 0.73-2.01 and 0.05-1.06 mg/kg, respectively. The relative average proportion of the three fractions was 3.83:2.90:1. The total content of arsenic was higher in the west part of the lake than that in the east part, while the oxidisable fraction of arsenic was higher in the east part of the lake. The contents of arsenic were closely related with the pollution loads of organic matter and nutrients of the drainage area, which indicated that the residual fraction of arsenic might be transformed to the soluble and reducible fractions. Furthermore, the pollution level of the sediments in Lake Chaohu was evaluated by Hak?nson’s index, Geoaccumulation index and Sediment quality guidelines. The results showed that arsenic pollution and its potential risk were lower. Therefore, it would not cause a serious threat to the surrounding environment and organisms in short term.