Background: Shenwu capsule is a pure traditional Chinese medicine developed by the Pharmacology Research Department of Xuanwu Hospital of Capital University of Medical Sciences (CUMS). It is served to treat senial dementia and has been proved to be effective in improving the learning and memory ability of many kinds of animal models with dementia. Objective: To observe the changes of learning and memory ability of model rats with Huntington disease(HD), the effects of shenwu capsule on it and explore its possible mechanism. Design: A randomized and controlled trial. Setting and materials: The trial was conducted at the Pharmacological Research Center of Xuanwu Hospital of CUMS. The materials were 60 male SD rats of clear grade. The rats were divided into the following groups: Control group, 3-nitropropionic acid(3-NPA) group, low-dose, middle-dose, and high-dose shenwu capsule groups, haloperidol group, and there were 10 rats in each group. In the process of the trial, there were 1 rat in control group, 2 in 3-NPA group and low-dose shenwu capsule group respectively, 3 in holoperidol group died. The cause might be inhalation asphyxia. Interventions: 20 mg/kg 3-NPA was injected intraperitonealy in each rat every other day for 20 days to make HD model. Rats in shenwu capsules of low dose (0.45 g/kg), middle dose (0.9 g/kg) and high dose (1.8 g/kg) were fed intragastrically for 25 days in corresponding groups. Rats in haloperidol group were fed with haloperidol from the day the HD model rats were made. The initial dose was 100 μg/kg per day, which was increased every other day till 1000 μg/kg per day. Main outcome measures: The time and distance of rats swimming in the Morris water maze; the latent time and times of mistake in step-through test; the bioactivity of Choline acetyl transferase(ChAT) in hippocampus; the number and surface of Glial derived neurotrophic factor (GDNF)cells in the CA4 part of hippocampus. Results: The time and distance of the rats with HD were significantly longer in Morris water maze. The swimming time of the rats in low dose and middle dose of shenwu capsule groups was 24.01% and 32.64% shorter respectively than that of the 3-PNA group. In step-through tests, the rats in 3-NPA group showed a shorter latent time than that of the rats in the control group before entering the dark chamber. The latent time in high-dose of and middle-dose shenwu capsule groups was longer than that of the rats in 3-NPA group. In hippocampus, the ChAT bioactivity of the 3-NPA group was lower than that of the control group. The ChAT bioactivity of high-dose shenwu capsule group and haloperidol group was higher respectively than that of the 3-NPA group(P < 0.01). The number of the positive GDNF cells and the total surface of positive cells in the area CA4 of hippocampus of the 3-NPA group were fewer than that of the control group and the total surface of positive cells was also less. The expression of positive GDNF cells in this area of the middle-dose shenwu capsules was markedly enhanced. Conclusion: There are significant damages in learning and memory ability of HD rats and shenwu capsule markedly improve their learning and memory abilities.