To study the mortality and risk of death on dementia among ageing population. A random sample including 2788 elderly residents was studied. Dementia was diagnosed under the two-phase procedure in 1997. In phase 1, questionnaire was administered, including the Mini-Mental State Examination (MMSE) tested. In phase 2, all the elderly who showed low MMSE score and some with normal MMSE score, were examined by neurologists. The clinical diagnosis of dementia was set up by two neurologists according to the criteria of DSM-III-R and NINCDS-ADRDA. The same sample was followed up in 2000 and 2004 the same way and data on deaths and causes was gathered. The overall time for follow-up was 7.25 years. 171 cases with dementia were diagnosed from 2788 subjects in 1997, with a crude death rate (CDR) of dementia was 7.8 per 1000 person-years and age-standardized CDR as 5.5 per 1000 person-years. The death rate was increased exponentially with age. In the dementia group, the total number of deaths was 133, with the CDR as 236 per 1000 person-years and the age-standardized CDR as 206 per 1000 person-years, in the end of the survey. In the non-dementia group, the total number of deaths was 680, with CDR as 40 per 1000 person-years and the age-standardized CDR as 31 per 1000 person-years. The difference in the two groups was statistically significant. The hazard ratio (HR) of dementia death appeared to be the biggest in the 60 - 74 - year group than the other groups. Data was analyzed with the Cox proportional hazards model after making necessary adjustment on potential covariates with the HR of dementia as 2.181 (95%CI: 1.751 - 2.717). The HRs were 2.524 (95%CI: 1.964 - 3.243) in Alzheimer's disease and 1.859 (95%CI: 1.213 - 2.850) in vascular dementia. The CDR and HR of dementia were higher than the non-dementia group in the aging population, showing that dementia was one of the most important risk factors on death in the aging population.