Objective: To study dynamic content changes of icariin in Er-xian decoctum in the decoction process.Methods: The content of icariin was determined by HPLC method.Hypersil-RDS C_(18)(4.6 mm× 200 mm,5 μm) column was used,with methanol∶water∶acetic acid(80∶70∶2) as the mobile phase and 1 mL/min as the flow rate.The detection wavelength was 270 nm.Transformation principle of icariin in Er-xian decoctum was investigated in different boiled time compared with single crude drug.Results: The linear range of icariin...