Abstract: A method of GC-MS determination of diethyleneglycol in toothpaste was proposed.The sample was pre-treated by microwave assisted extraction for 20 min at 120 ℃ using absolute alcohol as extraction solvent.After dehydration with anhydrous sodium sulfate,the extract was used for GC-MS analysis.The HP-INNOWAX capillary chromatographic column,with temperature elevation program from 130 ℃ to 250 ℃,was used in the GC separation,and the modes of electron bombardment ionization ion sourece (EI) and selective ion monitoring (SIM) were adopted in the MS measurements.Linear relationship between values of peak area and mass concentration of diethylene glycol was obtained in the range of 0.01-50.0 mg·L-1.Detection limit (3s/b) of the method was found to be 0.005 mg·L-1.Precision of the method was tested with 6 portions of 1.0 mg·L-1 diethylene glycol standard solutions,value of RSD found was 1.6%.Test for recovery was made by adding standard diethylene glycol to samples of toothpaste,results found were in the range of 95.0%-103.0%.