Abstract: Objective To explore the effect of diallyl disulfide (DADS) on hippocampal synapses and learning and memory abilities in a mouse model of A1zheimer’s disease (AD). Methods Mouse models of AD established by agglutinated Aβ1-42 injection in the lateral cerebral ventricle were randomized into 4 groups and treated with DADS at the daily doses of 0, 10, 50 and 100 mg/kg by gavage for 30 consecutive days. The learning and memory abilities of the mice were assessed with Morris water maze test; the structures of the dendritic spines and synapses in CA1 region of the hippocampus were observed under transmission electron microscope with silver staining; PSD95 and SYP protein and mRNA expressions in the hippocampus were detected with Western blotting and RT-PCR. Results Compared with the AD model mice, the mice treated with 50 and 100 mg/kg DADS showed enhanced learning and memory abilities in Morris water maze test. The dendritic spines and synapses in CA1 region of the hippocampus increased obviously and hippocampal expressions of PSD95 and SYP were enhanced in mice treated with 50 and 100 mg/kg DADS. Conclusion DADS at the daily doses of 50 and 100 mg/kg can improve the learning and memory abilities and increase the number of dendritic spines and synapses in the hippocampus in mouse models of AD.