Objective: To optimize the prescription of pH-triggered colon specific pellets of Sophora flavescens to evaluate drug release. Method: The pellet core was prepared by extrusion-spheronization method

taking sphericity

friability

yield

particle size distribution and dissolution as index to optimize the prescription of the pellet core.The prescription of pH-triggered coat was optimized by fluidized bed coating technology with drug release as index.The drug release in vitro was evaluated with paddle method. Result: The pellet core was prepared by extrusion-spheronization method with 4 times principal agent cellulose microcrystalline as diluent

6% CMS-Na and 28% water added to prepare soft material.The coat solution was prepared with Eudragit S100 as film-forming agent

95% alcohol as solvent

25% talcum powder and 20% triethyl citrate added.The accumulation leakage ratio of matrine and oxymatrine from the coat pellets in gastric juice and small intestinal juice in vitro was 21.6%

and 95.3% in colon juice. Conclusion: The prescription of pH-triggered colon specific pellets of Sophora flavescens was made;the quality of pellets was stable and the drug release of colon target was satisfactory.