into the residue, distribution, and composition of Dichloro-diphenyl-tricgloroethanes (DDTs) in sea water, sediment, and cultured shellfish in Dongshan Bay was carried out in spring(May) and summer(August), 2011. We also evaluated the contamination status and ecological risks. The results were as follows: irst, the DDT content in the sea surface layer varied from non-detectable(ND) to 25.7 ng/L in May and from ND to 36.7 ng/L in August, the average values were (6.08±3.02) ng/L and (16.30±4.78) ng/L, respectively; the DDT content in the bottom layer varied from ND to 30.6 ng/L and from ND to 36.7 ng/L, the average values were (7.75±2.07) ng/L and (13.30±5.12) ng/L in May and August, respectively. In general, the DDT concentration distribution in Dongshan Bay declined from the inner to outer bay and from the near- to far-shore. DDT concentrations in summer were higher than those in spring. Compared with other bays in China, DDTs pollution in Dongshan Bay was at a lower level status; however, it is likely that there has been a recent pollutant input in sites DS03 and DS11. Second, the DDT content in the sediment varied from 5.56−12.8 μg/kg, the average value was (9.00±5.34) μg/kg. The concentration declined from the inner to the outer bay. DDT residue in the sediment may have negative effects on organisms, the toxicity risk index varied from 25% 75%. Third, the DDT content varied among different species of cultured shellfish from 1.68‒26.60 μg/kg and the average was 15.70 μg/kg. The pollution index varied from 0.007 to 2.660, the average was 1.580. This exceeded the standard rate by 71.4% and the highest value was 1.66 fold. These results show that some shellfish have been contaminated by DDTs. This problem requires further attention and must be resolved.