Abstract: Water samples collected from the surface water of the Guanting Reservoir in Beijing of China were tested for 18 kinds of organochlorine pesticides(OCPs),using gas chromatography coupled with an electron capture detector(GC/ECD).Samples from 9 sampling sites were found to have residues of the 18 pesticides in the range of 10.06～87.37 ng·L^-1,and the concentrations of HCHs and DDTs were in the range of 3.93～38.94 ng·L^-1 and 3.71～16.03 ng·L^-1,respectively.It has been found that distribution of the organochlorine pesticides is closely related with soil cultivation style and water quality of the inflowing rivers.Wastewater discharged from the industrial zones in the upper streams and drainage from surrounding agricultural fields are major contributors of the pollution.Compared with other areas both at home and abroad,the Guanting Reservoir is lower in OCP concentration and its concentrations of DDTs and BHCs are below the upper limit of the National Standard for Surface Water Environmental Quality in China.