A high performance liquid chromatography-quadrupole ion trap tandem mass spectrometric(HPLC-QTRAP-MS/MS) method was developed for the quantification of 1-(2-hydroxyethyl) piperidine residue in flavoxate hydrochloride.After dissolved with 0.1% formic acid,the flavoxate hydrochloride sample was loaded onto an Agilent ZORBAX SB-Aq C18(2.1 mm×100 mm，1.8 μm) column to separate with a mobile phase of 0.1% formic acid-acetonitrile.The electrospray was operated in positive ion mode,and the sample was monitored in the select reaction monitoring(SRM) mode.As a result,the calibration curve of 1-(2-hydroxyethyl)piperidine showed a good linearity(r=0.999 7) in the range of 10-100 μg/L.The recoveries were in the range of 98.9%-106.8%,with relative standard deviations(RSDs) not more than 3.0%.The limit of detection(LOD,S/N=3) for the method was 6.0 mg/L,and the limit of quantitation(LOQ,S/N=10) was 20 mg/L.The method has the advantages of simple operation,high sensitivity and good reproducibility,and could be used for the detection of 1-(2-hydroxyethyl)piperidine in flavoxate hydrochloride.