[Objective] To investigate the flavonoids in the leaves of Rhododendron pulchrum sweet by high performance liquid chromatograph - electrospray ionization tandem mass spectrometry. [Method]The chromatographic separation was performed on a C18column ( 4. 6 mm × 250 mm,5 μm) . The mobile phase A waswater containing 0. 1% formic acid and mobile phase B was anhydrous methanol. Gradient eluted program was: 0 - 24 min,31% - 42% B; 24 - 30 min,42% -50% B; 30 - 35 min,50% - 60% B; 35 - 40 min,60% B. Injection volume was 20 μl; flow rate was 0. 7 ml / min; column temperature was 30 ℃ ; and detectionwavelength was 356 nm. Mass spectrometer conditions were ESI,anion mode scanning,drying gas temperature 350 ℃ ,drying gas volume flow ( N2) 10 L/min,nebulizing gas pressure 275. 8 KPa,capillary voltage 3. 5 kV,capillary export voltage 100 V,and mass scan range m / z 200 - 700. Data were collected in anionmode. [Result] Compared with the standard references and literature data,five flavonoids compounds were identified as hyperoside,isoquercitrin,avicularin,quercitroside and quercetin. [Conclusion]This method was rapid,accurate and effective which could be applied for the constituent identification of R. pulchrum,and provided theoretical basis for the application of R. pulchrum. [Objective] To investigate the flavonoids in the leaves of Rhododendron pulchrum sweet by high performance liquid chromatography - electrospray ionization tandem mass spectrometry. [Method] The chromatographic separation was performed on a C18column (4.6 mm × 250 mm, 5 μm). Gradients eluted program was: 0-24 min, 31% -42% B; 24-30 min, 42% -50% B; 30 - 35 min, 50% - 60% B; 35 - 40 min, 60% B. Injection volume was 20 μΐ; flow rate was 0. 7 ml / min; Conditions were ESI, anion mode scanning, drying gas temperature 350 ° C, drying gas volume flow (N2) 10 L / min, nebulizing gas pressure 275. 8 KPa, capillary voltage 3.5 kV, capillary export voltage 100 V, and mass scan range m / z 200 - 700. Data were collected in anionmode. [Result] Compared with the standard references and literature data, five flavonoids co mpounds were identified as hyperoside, isoquercitrin, avicularin, quercitroside and quercetin. [Conclusion] This method was rapid, accurate and effective which could be applied for the constituent identification of R. pulchrum, and provided theoretical basis for the application of R. pulchrum.