In order to explore the effects on the growth, physiological characteristics and astragaloside IV of A. membranaceus var. mongholicus under progressive drought stress, we potted 2yearold A. membranaceus var. mongholicus seedlings under 14 d progressive water control. The result showed that: (1) along with the soil water content decreased, RWC in the leaves of A. membranaceus var. mongolicus seedlings decreased, MDA content increased and the dry weight of roots and leaves decreased; (2) along with the period of drought stress continued, the activities of SOD, POD, CAT, APX and GR increased firstly and decreased then. In the roots, compared to control, they highly increased 72.1%, 108.6%, 178.0%, 299.4% and 303.4% respectively, and the contents of proline and soluble sugar increased observably. (3) The accumulation of astragaloside Ⅳ peaked at 12 d, increased 53.0% to control, then decreased. We concluded that with drought stress continued, the growth of A. membranaceus var. mongholicus seedlings was negatively influenced, but the antioxidant enzymes and osmatic adjustment substance could adjust themselves to avoid drought stress harm, to mainten the normal metabolic function of plants, and found moderate drought stress was beneficial to the accumulation of astragaloside IV, but this was limited when subjected to severe drought stress.