Abstract: A deuterated internal standard quantitative analysis method based on liquid-liquid extraction-ultra performance liquid chromatography-tandem mass spectrometry (LLE-UPLC-MS/MS) for simultaneous determination of 10 illicit drugs in wastewater was established.Wastewater samples were concentrated by liquid-liquid extraction with dichloromethane: ethyl acetate (1∶1), and separated by a linear gradient of 0.1% formic acid-5 mmol/L ammonium formate aqueous solution and acetonitrile on a C₁₈ column. The samples were then detected by ESI positive ion mode and multiple reaction monitoring mode (MRM) for quantitative analysis.All analytes had a good linear relationship (r ≥ 0.995 7) within the range of their respective standard curves; the limit of quantification was 1 ng/L (except amphetamine at 2.5 ng/L); the relative recovery rate ranged from 96.36% to 106.43%, and the intra- and inter-day precisions were less than 4.70%.This method is accurate, reliable and reproducible, and is suitable for the quantitative determination of 10 illicit drugs in wastewater.It is also suitable for wastewater with complex matrixes that affect solid phase extraction and enrichment.It provides a new analytical method for real-time monitoring of drug abuse.