[Objective] To determine the content of total flavonoids in Dendrobium officinale Kimura et Migo from Yueqing.[Method] Using rutin as reference substance,contents of total flavonoids in Dendrobium officinale Kimura et Migo from Yueqing were measured at 510 nm by UV spectrophotometry colored with NaNO2-Al(NO3)3-NaOH.[Result] Rutin concentration was linear with absorbance in the range of 0.011 1 to 0.066 7 mg/ml(R2=0.999 2);sample solution was stable within 12 h with RSD value of 0.15%;the established method was good in repeatability with RSD value of 3.12%.[Conclusion] The method was simple,accurate and stable,which could be used to determine the content of total flavonoids in Dendrobium officinale Kimura et Migo.