As increasing number of studies have clearly demonstrated that smoking increased the risk of dementia in the elderly, studies on the relationship between passive smoking and cognitive impairment or senile dementia has been done recently. Controversy still exists regarding the role of secondhand smoking in developing dementia because of few studies. This paper provides epidemiological basis for prevention of tobacco control movement and development of senile dementia by studying the related literature at home and abroad, summarizing passive smoking exposure assessment and senile dementia screening and diagnosis method, and combing the relationship between passive smoking and cognitive impairment or senile dementia.