Abstract: HPLC was applied to the determination of geniposide, berberine hydrochloride, baicalin and emodin in Siji Sanhuang pills. The sample was extracted ultrasonically with methanol. The extract was separated on a Phenomenex Luna C₁₈ column with gradient elution using acetonitrile and 0.1% (φ) formic acid solution as mobile phase. Diode array detector was used with the detection wavelengths of 240, 345, 278, 287 nm, for geniposide, berberine hydrochloride, baicalin and emodin, respectively. Linearity ranges of geniposide, berberine hydrochloride, baicalin and emodin were 7.66-76.6, 8.99-89.9, 3.87-38.7, 4.45-44.5 mg·L^-1, respectively. The detection limits (3S/N) were 0.27, 0.038, 0.037, 0.048 mg·L^-1, respectively. Recovery rates obtained by standard additon method ranged from 96.3% to 99.5%, and RSDs (n=6) were in the range of 1.7%~2.4%.