Objective：To study the histopathological and ultrastructural changes in the hippocampus of rats with vascular dementia（VD） by light and electron microscopy. Methods：Totally 60 SD rats were randomly divided into sham-operated group（n=10） and model group（n=50）. VD models were constructed by permanent bilateral common carotid artery ligation and 10 rats were killed at each time point（1，7，14，21，28 d） after operation（1，7，14，21，28 d model groups）. Rats in sham-operated group were only separat－ed，not ligated bilateral common carotid arteries. Histopathological and ultrastructural changes in the hippocampus were observed with microscopy and electron microscopy respectively at each time point with 10 killed VD rats. Results：Numbers of neurons in CA1 re－gion of rats’ hippocampus in model group were decreased significantly compared with those in sham-operated group，being the fewest in 14 d model group（P=0.000）. Ultrastructural changes demonstrated the pyknosis and degeneration of neurons，however，with the re－covery of cerebral blood flow supply，numbers of neurons were gradually increased and less neuron degeneration was observed with electron microscopy. Conclusions：At early stage of chronic cerebral hypoperfusion，degereration of neurons in the hippocampus is re－versible，which provides theoretic basis for early clinical treatment of chronic cerebral hypoperfusion in prevention of VD.