Objective To develop a method for the determination to organochlorine pesticides by gas chromatography-mass spectra-mass spectra.Methods The temperature of inlet was 250 ℃,the injection volume was 1 ?l,without split injection.The temperature of EI source was 300 ℃,the ionization energy was 70 eV,solvent delay time was 3.75 min,transfer line temperature was 280 ℃.181,235,246(m/z)were selected as parent ion,and 145,165,176(m/z)were sub ion.Results In the range of 0-50 ?g/L,every component had a good linearity,r≥0.99,the limit of detection≤0.01 ?g/L.Its average rate of recovery was in the range of 86.1%-101.8%,and the relative standard deviations(RSDs) were between 4.41%-8.07%.Conclusion Gas chromatography-mass spectra-mass spectra is more precise for the qualitative and quantitative determination of trace organochlorine pesticides residues in drinking water.