Abstract: A detection method of octachlorodipropyl ether(S-421) in tea using gas chromatograph with electron capture detector was reported. Octachlorodipropyl ether was extracted from tea samples using n-hexane-acetone(22∶ 3,V/V),purified with celite 545- sulfuric acid (1g-0.4mL) using hexane as an eluent. At the spiking level of 0.01 ~1.0 mg/kg,the recovery of this method was in the range from 93.0% to 96.6% with standard deviation of 1.70~4.05%,and the LOQ was 0.010 mg/kg. To identify the sources of octachlorodipropyl ether in tea that are commonly used for tea trees were examined,including 25 chemical pesticides,11 biological pesticides,9 fertilizers and 7 leaf fertilizers. No residues were found in the above material.It was found that the main sources of octachlorodipropyl ether in tea may be the absorption from the combustion of the mosquito coils and the aerosols.