A　widely　used　Chinese　cardiotonic　proprietary　medicine,　compound　Danshen　dripping　pills　(CDDP,　Fufang　Danshen　Diwan)　has　also　begun　to　be　used　for　treatment　of　vascular　dementia　(VaD).　We　tried　to　explore　the　mechanism　of　CDDP　action　in　this　case.　A　VaD　experimental　model　was　built　in　rats　by　bilateral　ligation　of　the　common　carotid　arteries.　The　cognitive　ability　of　experimental　animals　was　evaluated　in　the　Morris　water　maze　test.　Synaptic　ultrastructural　changes　in　the　hippocampus　were　detected　by　transmission　electron　microscopy;　expression　of　PSD-95　mRNA　in　the　hippocampus　was　examined　using　hybridization　in　situ.　The　latter　index　(mRNA　expression)　in　the　VaD　group　was　significantly　lower　than　those　in　the　CDDP　and　sham-operated　groups　(P　＜　0.05).　CDDP　treatment　considerably　improved　disturbed　ultrastructural　synaptic　characteristics　in　the　hippocampus　of　VaD　rats.　The　mean　escape　latency　in　the　Morris　water　maze　test　was　significantly　shorter　in　CDDP-treated　VaD　rats,　compared　with　that　those　of　the　VaD　group　(P　＜　0.05).　In　the　CDDP　group　compared　to　the　VaD　one,　escape　strategies　improved　from　edge　and　random　searches　to　more　linear　swim　pathway　(P　＜　0.05).　Thus,　decreasing　expression　of　PSD-95　plays　an　important　role　in　the　pathogenesis　of　VaD.　CDDP　treatment　improves　the　learning　and　memory　ability　of　VaD　rats　by　improving　neural　synaptic　ultrastructural　characteristics　and　increasing　expression　of　PSD-95　mRNA　in　the　hippocampus.