Abstract: A sohxlet- extraction- gas chromatography-(tandem) mass spectrometry (GC-MS/MS) as a tool for 20 organochlorine pesticides residue analysis in lake sediment was developed. Chromatographic column of silica gel and alumina was employed to remove impurities in the concentrated extraction by different ratios of hexane and dichloromethane eluents. Then the concentrated eluent was analyzed by the gas chromatography-(tandem) mass spectrometry. The matrix interferences were eliminated owing to Multiple Reaction Monitoring (MRM) mode of GC-MS/MS together with the Chromatographic column of VF-1071. The pretreatment was simplified and accurately qualitative and quantitative analysis of the target compounds was supplied. This method was of high sensitivity and showed a good linearity. Recoveries obtained by analyzing the spiked standard in matrix were in the range of 79.76%-115.04%, whereas the relative standard deviation (RSD) values were ranging from 1.15% to 14.08%. The method detection limit was between 0.002 4 and 0.513 7 μg/kg and limits of quantification of the method were between 0.007 and 1.541 μg/kg. This new method is stable and reliable for trace analysis of organochlorine pesticides residues in the sediment.