The dynamic of physiological state and contents of 4 flavonoids (calycosin, calycosin7oβDglucoside, formononetin and ononin) in roots, stems and leaves were studied with the triennial Astragalus membranaceus (Fisch.) Bge. var. mongholicus (Bge.) Hsiao, under the continuous drought stress, by pot culture simulated drought conditions, at greenhouse in Inner Mongolia University. The result shows that: (1) calycosin and calycosin7oβDglucoside are distributed and obvious difference in the three different parts, which the content of calycosin was leaf > stem > root, but the calycosin 7oβDglucoside was root > leaf > stem. (2) The response of the four flavonoids in the same organ under drought stress were different. The contents of calycosin7oβDglucoside and ononin were increased during 8-12 d and then decreased in roots under drought stress. It is interested that the contents of calycosin was accumulated during 4-8 d, but calycosin7oβDglucoside has few changes. Those results indicated that the contents and distributions of four kinds of flavonoids are diverse in different organs, and the response to drought stress is difference in the same organ. The moderate drought stress improved and severe drought stress would have a negative effect on the accumulation of flavonoids in A. membranaceus var. mongholicus (Bge.) Hsiao.