AIM:To develop a new method to determine cucurbitacin B in Pedicellus Melo by capillary zone(electrophoresis(CZE).) METHODS:All the samples were analysed on a fused silica capillary(75 cm?75 ?m I.D.) by using 50 mmol/L sodium borate solution(containing 5% acetonitrile) as the background electrolyte with the running voltage at 12.0 kV and detection wavelength of 265 nm.And clorprenaline hydrochloride was applied as the internal standard. RESULTS:The results showed a good linear correlation between relative peak area of cucurbitacin B(y) and its concentration(x) over the range of 0.15～1.2 mg/mL.Regression equation was y=(0.003 4x)+0.058,r=0.999 7,and the average recovery for baicalin was 100.2% with the RSD at(2.11%). CONCLUSION:The method is rapid,simple,reproducible and produces low pollution.It serves as a novel way to determine cucurbitacin B.