The purposes of this study were to measure disparities of age structure between people with an intellectual disability and general population, and to explore the difference of demographic characteristics between these two populations by using data from a population based register in Taiwan. Data were analyzed by SPSS 20.0 statistical software. Results found that the gender and mean age were significantly different between people with an intellectual disability and general population (mean age: 28.86 years vs. 35.26 years; p less than 0.001). The shape of the pyramid in general population tended to be fatty in the middle age, and intellectual disability population was more populous in the younger age. Furthermore, there were very few people with an intellectual disability can live more than 65 years old (3%) while there were nearly 10% of the general population were the elderly. The results also showed that two groups were different in marital status, educational levels, family status of veteran and aborigine (p less than 0.001). As the premature aging and short life span of people with an intellectual disability, this study suggested that the government authority should initiate necessary assistance for this group of people in the future. (Contains 4 tables and 2 figures.)