The animal models were conducted to activity screening of different ethanol fraction from Radix Astragali. Eluted from the macroporous adsorptive resins, the potential active fraction that had vasodilative effects was isolated and purified by high-speed counter-current chromatography (HSCCC) using gradient elution. The solvent system was composed of chloroform-methanol-acetic acid-water (2 : 1 : 1 : 1, v/v/v/v). The flow rate was 1.0 mL min(-1) initially and changed to 2.0 mL min(-1) at 300 min. Four flavonoids named calycosin-7-O-β- D -glycoside (a), formononetin-7-O-β- D -glycoside (b), calycosin (c) and formononetin (d) with purity over 94% were obtained and then identified by (1)H NMR and (13)C NMR.