Our study was to demonstrated whether Tenuigenin，an extract of Polygala tenuifolia willdenow，can decrease A . And its mechanism.[Method] Tenuigenin was extracted from air-dried roots of Polygala tenuifolia willdenow .The roots (1000g) were ground and refluxed with ethanol (95％ v/v) for three times (3h each)，the extract was combined and evaporated in vacuo，and the yielded residue was suspended in water and extracted successively with petroleum，chloroform and n-butanol. The n-butanol extract was subjected to a macroporous resin D101 column，the adsorbed material was eluted successively with H2O，then 20，70 and 95％ ethanol，the 70％ ethanol eluate was evaporated to dryness (Tenuigenin fraction). Tenuigenin was composed of Tenuigenin A，B，C，D，E，F，G，which were identified by chromatogram.