Objective A simultaneous determination method for five benzodiazepines (nitrazepam, diazepam, oxazepam, chlordiazepoxide, clonazepam) in drinking water was developed using ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Methods Samples were concentrated and purified with MCX solid-phase extraction cartridge. The chromatographic separation was achieved using an ACQUITY BEH C₁₈ (2.1 mm×100 mm, 1.7 μm) column with methanol and water as mobile phase. The targets were analyzed with ESI operating in positive multiple reaction monitoring (MRM) mode. Quantification was performed by matrix-matched standard calibration. Results Satisfactory linearity (r²>0.999) was obtained for all targets, with the limits of quantification (LOQs) ranged in 0.050-0.500 ng/L. Average recoveries at three spiked levels were 78.2%-108.0%, with relative standard deviations (RSDs) less than or equal to 12.4% (n=6). The developed method was used to analyze 96 drinking water samples, in which 51 samples were detected containing diazepam and 13 samples containing oxazepam. The concentrations were