The contents of diehloro diphenyl triehloroethanes(DDTs) in surface water from fifteen sampling sites in Lake Chaohu were meusured by solid phase extraction-gas chromatograph-electron capture detecmr(SPE-GC-ECD).The DDTs residues, possible sources.as well as potential ecological and health risks were analyzed. The following results were obtained:1) the average content in the lake water was 9.98±4.73 ng/L, witIl the range of 1.52-21.79 ng/L.2) The sources of DDT were mainly from historical usage of technical DDTs pesticides and recent usage of other pesticides with larger ratio of o,p'-DDT to p,p'-DDT(such as dicofol).The eastern water source area was mainly under anaembie conditions.3) The water ecological risk to all species at various sample sites by Species sensitivity distribution(SSD) model was very low with the range of 8.3×10^-15-2.1×10^-8.Marsin of safety(MOSl0) of DDT for invertebrates, fish, crustaceans, and insects & spiders Was 24.5%, 15.6%, 31.9%, 17.5%, 46.9% and 18.7%, respectively. The risk assessment results by three methods were with good agreement, showing that the ecological risk of DDT to invertebrates(e. g. Crustaceans) was higherthan thatto vertebrates(e. g. fish), and that the DDT ecological risk was very low in Lake Chaohu.4)DDTs' carcinogenic risk was lower than 10^-6.and its non-carcinogenic risk was far less than 1, implying that it would not cause significant carcinogenic and non-carcinogenic human health risk when using the lake water as drinking and bathing.