The purpose of this study was to observe the longitudinal change of cognitive function of elderly people. Over 180 community-dwelling elderly people were tested with MMSE at baseline and followed up five years later. About 42.9% of 1,225 people who had cognitive impairment at baseline survey were found to be dead in follow-up survey, and the death rate was much higher than that of cognitive intact person, which was 19.45%. Among 1,335 cases who finished MMSE test twice the mean score of MMSE at follow-up was 23.35, which was lower than original mean score (23.77). The rate of people identified as abnormal by education adjusted cutoff point also increased from 8.24% to 17.8%. Viewed individually 51.9% of them remained stable in MMSE score, 24.5% decreased and 23.6% increased after five years. Old people aged 70 or above, less educated, and people who scored around or lower than cutoff point were more likely to decline. Conclusion: The performance of MMSE has certain predictive value to the outcome of elderly people, and cognitive decline in community lived people is quite slow.