According to the World Health Organization (WHO) and Alzheimer Disease International (ADI), there are at least 35.6 million people suffering from dementia in the world. Mild cognitive impairment (MCI) is considered as a risk state or a prodromal of dementia. This paper aims to make further exploration into the risk factors of mild cognitive impairment, analyzing the longitudinal data of three waves of surveys in 1999, 2003 and 2007 from 'Taiwan Longitudinal Study on Aging' (TLSA). The hierarchical linear model (HLM) is applied to analyze samples from the TLSA of Taiwan's elderly 65 years old and over in 1999. Empirical results suggest that cognitive function worsening differs among individuals, but clearly increases with age. Depressive symptoms show statistically positively significance but educational attainment show the opposite direction, whereas gender, marital status, ethnic, health behavior, and family support are all not statistically significant.