Abstract: Clenbuterol (NAB-365 ) is one of the active ingredients contained in Compound Tablet of Yuanhuatong, but it couldn't be determined owing to it's microamount and interference of Ynanhuatong (total flavones crude extract obtained from Flos Genkwa). A suitable method for determination of μg amount of clenbuterol contained in the compound tablets is described by a six-point orthogonal functions spectrophotometryto eliminate the interference of yuanhuatong.The proposed method involves an addition of a certain amount of NAB-365 to the sample being tested, a suitable extraction and a subsequent spectrophotometric determination with six wavelengths from 292-3O2 nm at 2 nm intervals, and a calculation of the quadratic polynomial regression coefficient, d_2.