Capillary electrophoresis(CE) method has been developed for the determination of flavonoids and the content of rutin,quercetin,kaempferol,Chlorogenic acid in water chestnut.Based on the effects of composition and concentration of running buffer,pH,separation temperature and separation voltage,the optimal conditions were found as: the running buffer consisted of 20 mmol/L KH2PO4-20 mmol/L borax,the UV detection wavelength was 202 nm,separation voltage was 24 kV,separation temperature was 30℃.Under these optimal chromatographic conditions,the four flavonoids can be separated within 7 minute.Moreover,the calibration curves of the concentrations of four flavonoids and their corresponding peak areas showed good linearity in the range 3.125 from 100 mg/L.The correlation coefficient was above 0.999.The RSD of migration times was between 0.78% and 0.98%,and the RSD of peak areas was between 6.5% and 8.6 %.At the spiked concentration of 5.0,10.0,20.0 mg/kg,the average recoveries of the four flavonoids ranged from 80% to 98%.This method is very simple,rapid,good repeatability and can be applied to the determination of four flavonoids in plants.