D chiro inostiol in buckwheat was determined by high performance capillary electrophoresis (HPCE) with ultraviolet detector, with100 mmol/L borate buffer, voltage 10kV and detection wavelength 195 nm. The results showed that the linear range was 0.1～150 mg/mL with correlation coefficients more than 0.999 and the detection limit less than 0.02 mg/mL (RS/N=3).The average recoveries were in the range of 9%～108%, with the relative standard deviation (RSD) 4.3%. This method is convenient, accurate and reliable, which can decrease the cost and pollution, increase the efficiency with aqueous solution as moving phase.