Recently, because of advancing in medical technology, longevity of people has been increasing. As a result, population structure also ages fast. Aging population has a great impact on the country's financial, economic, sanitation, and social systems. China’s population accounts for one-fifth of the world, and affects the world more than ever. Although China’s aging issue happened less than 10 years, it almost catches up with developed countries. This paper focuses on the impact that aging population brings to health-care expenditure. Because China’s data is not complete, we use Taiwan’s data to estimate. We apply Taiwan’s estimation result to China’s future health-care expenditure, and we discuss what it means in the society. The results show that China's medical costs will grow over time, consistent with the growing of its aging population. Total medical expenses grow from 3.94 trillion RMB in 2015 to 59.74 trillion RMB in 2050, increasing by more than 15 times. However, surprisingly, the medical expenses of elderly population increase by more than 30 times, growing from 1.02 trillion RMB in 2015 to 30.35 trillion RMB in 2050. This result is similar to Taiwan’s estimated medical expenses. The percentage of China’s national health expenses accounts for 5.86% in 2015 and will grow to 11.53% in 2050 of GDP. The increasing of health spending will definitely affect a country’s finance. In addition, China’s one-child policy accelerates aging problem, so China has to establish a sustainable health-care insurance system in order to make ends meet in long term.