Objective To investigate the smoking and cognitive function of elderly people in some geracomiums of Chongqing city and to explore the effects of smoking on the cognitive function. Methods The stratified random sampling method was adopted. According to the inclusion and exclusion criteria, 230 old people (age≥60 years) from 11 geracomiums of Chongqing city were selected and surveyed by the nutrition health questionnaire for old people and Minimum Mental State Examination (MMSE). The results were analyzed by the χ2 test and Fisher exact probability method. Results MMSE was performed for 230 qualified old people. Among them, 151 people (65.65%) were with the cognitive impairment. The relationship of current smoking and cognitive impairment was statistically significant (χ2=12.897 7，P=0.000 3), while the relationship of past smoking and cognitive impairment was no statistically significant (χ2=1.330 0, P=0.248 8). The relationship of the period of current smoking and the cognitive impairment was statistically significant (χ2=16.887 9, P<0.000 1). Conclusion Current smoking is a risk factor of cognitive impairment of old people. The risk increases with the period of smoking. Quitting smoking is an effective measure to decrease the incidence of cognitive impairment.