Objective To establish a method of HPLC assay for determining emodin in Yishi Granules.Methods The effective components in Yishi Granules were determined by HPLC.The chromatographic conditions were as follows:Alltech C18 column(250 mm? 4.60 mm,5 ? m),mobile phase consisting of methanol-0.1 % phosphoric acid(80:20),flow rate at 1 mL? min-1,detecting wavelength being 254 nm,and the column temperature being 30 ℃.Results The separation and the linearity were good in the range of 32.8～ 131.2 ?g,r=0.999 9.The average recovery of emodin was 100.20 %,and RSD=1.52 %(n=6).Conclusion The quantitative method for determining the active components of Yishi Granules is simple,feasible and reproducible,and is beneficial for the quality control of Yishi Granules.