Objective: To observe the effect of compound preparation of milkvetch root and breviscapine (HDs) on the activity of superoxide dismutase (SOD) and lactate dehydrogenase(LDH), the concentration of malondialdehyde (MDA) in blood and brain and memory impairment in Alzheimer's disease rats.Methods: The rats were randomly divided into 5 groups (10 rats /group): the normal control group, Alzheimer's disease (AD) model group induced by AlCl3(5 mg·kg -1·d-1,ig) and D-gal (40 mg·kg-1·d-1,ip), and 3 AD groups respectively treated with different drugs including piracetam (0.15 g·kg-1·d-1,ig), HDs1(1.5 ml·kg-1·d-1,ip) and HDs2 (3 ml·kg-1·d-1,ip).After 90-day treatment, the step-down test was used to detect the learning and memory ability, and SOD and LDH activity and MDA concentration in blood and brain were examined as well.Results: Compared with that in AD model group, the ability of learning and memory was improved, the activity of SOD and LDH increased significantly, the concentration of MDA decreased significantly in blood and brain in HDs treated groups.The differences were statistically significant (P<0.05 or P<0.01), but they were not restored to normal levels.Some indexes of HDs2 group were better than those of piracetam positive control group and HDs1 group (P<0.05 or P<0.01).Conclusion: HDs can effectively reduce MDA concentration, increase SOD and LDH activity in blood and brain, and improve the ability of learning and memory of AD rats.