Based on the panel data of China's prefecture-level cities in 2000, 2010, and 2020, this paper examines the spatial effects of population ageing on technological innovation and explores the heterogeneous impacts of ageing on technological innovation at different stages of social and economic development. The analytical results of the spatial Durbin model exhibit a robust inverted U-shaped relationship between population ageing and local technological innovation, as well as a U-shaped relationship between population ageing and neighbors' innovation. Furthermore, the threshold regression models indicate that, at the stage of low urbanization rate and insufficient supply of health services, population ageing imposes a significantly negative impact on technological innovation. With higher urbanization and a more adequate supply of health services, population ageing would stimulate innovation. Therefore, against the backdrop of the irreversible ageing process, promoting the urbanization process and improving the health care system will effectively attenuate the discouraging effects of ageing on innovation.