An HPLC method using unmodified silica with reversed-phase eluents was developed for the determination of DL-tetrahydropalmatine in Corydalis Yanhusuo W. T. Wang and its set prescription preparations. The mobile phase was a mixture of methanol and 2 mmol/L phosphate buffer (75:25, v/v). The result was calculated by external standardization. The method is simple, rapid and precise, and could also be used for the separation and determination of alkaloids in other crude drugs and preparations.