A quantitative method for determining levels of three bioactive compounds based on pattern recognition was developed and fully validated for the quality control of Alismatis Rhizoma (AR) by HPLC. Separation conditions were optimised using an Optimapak $C_{18}$ column ($250mm{ imes}4.6mm$, 5 ${mu}m$) with a mobile phase of acetonitrile and 0.1% aqueous phosphoric acid and detection wavelengths of 205 and 245 nm. Method validation yielded acceptable linearity ($r^2$ > 0.9998) and percent recovery (98.06%-101.71%). Limits of detection ranged from 0.08 to 0.15 ${mu}g/mL$. Levels of the three bioactive compounds, alisol C acetate, alisol B, and alisol B acetate, in AR were 0.07-0.45, 0.38-10.32, and 1.13-8.59 mg/g dried weight, respectively. Pattern analyses based on these three compounds were able to differentiate Chinese and Korean samples accurately. The results demonstrate that alisol B and its acetate may be used as marker compounds for AR quality and can be regulated to no less than 0.36 and 1.29 mg/g of dried sample, respectively. The method described here is suitable for quantitative analyses and quality control of multiple components in AR.