Objective: Establishing a method of HPLC for quantitative determination of formononetin in the effective fraction of Qishao formula to further characterize the content of isoflavones in the effective fraction of Qishao formula. Method: The procedure of HPLC-PDA was performed on the chromatographic column of ODS HYPERSIL(4.6 mm×250 mm

5 μm)

and the mobile phase in the gradient elution program was acetonitrile-phosphoric acid solution(0.2%)

the column temperature was at 35 ℃.The flow rate was 1 mL·min-1

and the detection wavelength was at 249 nm. Result: The regression equations was as follows: Y＝6×106+06X-16 320(r=0.999 8).Formononetin showed good linear relationship from 0.036 48 to 0.364 8 μg.The average recovery was 98.70%

(RSD 0.77%). The contents of formononetin in three batches of the the effective fraction of Qishao formula was 0.81

0.74

0.63 mg·g-1

respectively. Conclusion: The method is easy and accurate with higher repeatability

which can be used in the quality control of the effective fraction of Qishao formula. It will provide support to control of the isoflavones in the effective fraction of Qishao formula. At the same time to lay the foundation for controlling its quality effectively.