Based on panel data collected from 41 countries over the period 2007-2017, this paper analysis how population ageing affects technological innovation through three aspects from the perspective of human capital: the loss of knowledge and talents; reverse force and knowledge spillover. In this paper, the technological innovation index (TII) is calculated by using the factor analysis method. Further with this, a fixed-effects regression model is applied to discover that population exerts a significant positive effect on technological innovation through reverse force, while exerts negative effects on technological innovation through the loss of knowledge and talents and knowledge spillover.