Abstract: Objective - - To establish a pre column derivatization high performance liquid chromatography method for detecting Methods dimethyl sulfate (DMS) in workplace air. DMS in workplace air was collected with mercaptopyridine impregnated （ silicone tube. The derivative of DMS and mercaptopyridine was eluted by mobile phase phase A: water, phase B: acetonitrile, ∶ the volume ratio was 40 60) , and separated with a C18 column, then detected with diode array detector and quantitated by a Results - standard curve. The linear range of DMS was 0.17 40.00 mg/L, with the correlation coefficient of 0.999 95. The detection limit and the lower limit of quantitation were 0.05 and 0.17 mg/L respectively. The minimum detection concentration and minimum quantitation concentration were 0.02 and 0.04 mg/m³, respectively (air sample volume of 4.5 L, 1.0 mL sample - - - solution). The average desorption efficiency was 98.40% 102.00%. The within run and between run relative standard deviations - - were 0.61% 3.92% and 1.71% 6.00%, respectively. The samples could be stored at room temperature for at least 14 days. Conclusion This method can be used to detect DMS in workplace air.