Abstract: A rapid analytical method for the determination of dezocine and pethidine in hair samples using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established.After cleaned hair was extracted by grinding with methanol and ultrasonic, the final solution was analyzed by UPLC-MS/MS.The targets were gradient eluted on a Waters Acquity BEH C₁₈ (2.1 mm × 100 mm, 1.7 μm) column with 0.1% formic acid-water and methanol as mobile phase at a flow rate of 0.4 mL/min.The ESI⁺ ion source and multiple reaction monitoring (MRM) were used to select the qualitative and quantitative ion pairs of dezocine and pethidine.Dezocine and pethidine showed good linearity in the range of 0.01-8 ng/mg, with the limit of detection of 0.005 ng/mg and the LOQs of 0.01 ng/mg.The accuracy, precision, matrix effect, extraction recovery, and stability all met the requirements.The established method is simple, rapid, and accurate for the qualitative and quantitative determination of dezocine and pethidine in hair, which can be applied in the case analysis of dezocine and/or pethidine abuse.