[Objective] To simultaneously determine contents of chlorogenic acid,rutin,quercetin and kaempferol in leaves of Eucommia ulmoides Oliver at different tree age by high performance liquid chromatography method(HPLC).[Method] Mixed solution of methanol and 0.4% phosphoric acid solution in different volume ratio were used as mobile phase in the gradient elution,whose flow rate was 1.0 ml/min.Using Shim-pack VP-ODS(4.6 mm×150 mm,5 μm)as chromatographic column,the bioactive constituents were analyzed qualitatively base on their retention times combination with ultraviolet absorption spectra.The quantization analysis was carried out by external standard method with detection wavelength at 360 nm and column temperature at 40 ℃.[Result] The linear ranges of chlorogenic acid,rutin,quercetin and kaempferol were 4.63-92.65(r=0.999 8),0.714-14.285(r=0.999 9),0.101-2.066(r=0.997 0)and 0.043-0.886 μg/ml(r=0.998 0),respectively.The recoveries of bioactive constituents were 98%-101.5%,96%-98.4%,94%-101% and 92%-96% respectively.[Conclusion] The contents of four kind’s bioactive constituents in leaves of Eucommia ulmoides Oliver at different tree age were analyzed by way of variance analysis and multiple comparisons.Considering the content of chlorogenic acid,leaves of Eucommia ulmoides Oliver about three-year-old tree age was the best. [Objective] To determine the content of chlorogenic acid, rutin, quercetin and kaempferol in leaves of Eucommia ulmoides Oliver at different tree age by high performance liquid chromatography method (HPLC). [Method] Mixed solution of methanol and 0.4% phosphoric acid solution in different volume ratio were used as mobile phase in the gradient elution, whose flow rate was 1.0 ml / min. Using Shim-pack VP-ODS (4.6 mm × 150 mm, 5 μm) as chromatographic column, the bioactive constituents were analyzed qualitatively base on their retention times combination with ultraviolet absorption spectra. The quantization analysis was carried out by external standard method with detection wavelength at 360 nm and column temperature at 40 ° C. [Result] The linear ranges of chlorogenic acid, rutin, quercetin and kaempferol were 4.63 -92.65 (r = 0.999 8), 0.714-14.285 (r = 0.999 9), 0.101-2.066 (r = 0.997 0) and 0.043-0.886 μg / ml (r = 0.998 0), respectively.The recoveries of bioactive constituents were 98% -101.5%, 96% -98.4%, 9 4% -101% and 92% -96% respectively. [Conclusion] The contents of four kind of bioactive constituents in leaves of Eucommia ulmoides Oliver at different tree age were analyzed by way of variance analysis and multiple comparisons. Consumption of the content of chlorogenic acid , leaves of Eucommia ulmoides Oliver about three-year-old tree age was the best.