An ultra high performance liquid chromatography-tandem mass spectrometric(UPLC-MS/MS) method was developed for the determination of 9 sedative hypnotic drugs(chormezanone,triazolam,alprazolam,estazolam,diazepam,nitrazepam,oxazepam,lorazepam,chlordiazepoxide) in health foods, and the dissociation pathways of nine drugs were studied by electrospray ion mass spectrometry.After extracted with methanol,the analyses were separated on a Zorbax SB-C18(3.5 μm,2.1 mm×150 mm) chromatographic column by gradient elution using a mixture of acetonitrile and 0.1% formic solution as mobile phase at a flow rate of 0.3 mL/min.Detection was performed by electrospray ionization in the positive ion mode under multiple reaction monitoring(MRM) mode,and quantified with matrix standard curve.As a result,the calibration curves for all target compounds were linear in the range of 0.5-50 μg/L with correlation coefficients(r2) larger than 0.99．The limits of quantitation(LOQ,S/N≥10) were in the range of 1.6-9.2 μg?kg-1.The recoveries for all the drugs were 78.1%-101.2%.The intra and inter day precisions values at three spiked levels were between 1.4%-9.7%and 2.0%-11.2%,respectively.With strong selectivity,high sensitivity,easy operation and rapid detection,this method could be used to detect 9 kinds of illegally added sedative drugs in health foods.Moreover,the study of mass spectrometric behaviours and ion fragmentation patterns of nine drugs could provide a reference for the qualitative identification and quantitative analysis.