Objective: To establish a accurate method for determination of iso-orientin in Commelina communis L.and compare the determination on different growing periods in order to determine the optimal harvesting time.Method: The Agilent TC-C18（4.6 mm × 250 mm

5 μm） was used.The mobile phase was acetonitrile-0.1% phosphoric acid solution（15∶ 85） and the flow rate was 1 mL·min-1 with UV detected.Result: The linear ranges of were at 0.08～1.00 μg

the average recoveries were 101.2%.Different growth stages have a significant effect for determination of iso-orientin and the levels of maturity is a highest.Conclusion: The method is convenient

effective and suitable for determination of iso-orientin in C.communis.It provides the basis for the quality standards and reference in order to determine the optimal harvesting time.