Objective: To investigate the relationship between population age growth and healthcare expenditure so as to provide references for controlling health expenditure and improving medical insurance system. Methods: Based on the panel data of China Family Panel Studies (CFPS) in 2012, 2014, 2016 and 2018, the nonlinear impact of population age change on healthcare expenditure are explored by establishing a dynamic panel threshold effect model. Results: There is a threshold value such that when the age crosses the threshold value of about 49 years old, the elasticity coefficient of the effect of population age growth on total medical expenses becomes larger, ranges from 2.372 to 5.422. The elasticity coefficient of the age of urban residents nearly tripled after crossing the threshold, increasing from 2.643 to 7.617; the elasticity coefficient of the age of rural residents changed little, increasing from 1.846 to 2.485. Conclusion: With the deepening of population aging, the total health expenditure will face greater growth pressure. Therefore, it is needed to speed up the connotation expansion and integration of the medical and health system in combination with the demand of the current aging background.