Objective  The purpose of the investigation was to study the risk factors of senile dementia and to provide a scientific basis for making strategy of senile dementia.Methods  A sampling survey of 158 old people(male?73,female?85)  for their physical condition and it’s influencing factors have been done in Nanjing.The indices adopted included  health appraisal of oneself,psychological trauma,mental health,happiness degree,ability of taking care of oneself,Bech  H table,senile dementia screening scale table.Epi Info and SAS software were used for univariate and multivariate analysis.Results  Univariate analysis shows that the indices of age,sex,occupation,massiage,education and cerbgral haemorrhage history are closely related to the incidence of senile dementia.From multivariate analysis,we can see the older the age and the lower the culture level can lead to the higher incidence of senile dementia.Conclusion  The senile dementia is related to social psychological  factors.