A technique for simultaneous determination of 13 phenoxy acid herbicide residues in soybean was developed.Phenoxy acid herbicides were extracted with acetonitrile-50 mmol/L HCl(volume ratio was 7 3),followed by liquid-liquid partition with n-hexane.The soybean extract was further cleaned up by anion exchange column and derivatized with pentafluorobenzyl bromide.The resulting esters were determined by gas chromatography equipped with electron capture detector.The pre-treatment method was critically examined.Recoveries of two fortified levels(0.01 and 0.1 mg/kg)were above 70%.and the coefficients of variation were less than 20%.It showed that this method can meet the requirements of multi-residue analysis in the inspection of import/export soybean commodities.