Abstract: China is currently undergoing a critical transition from a population quantity dividend to a population quality dividend. Given the significant changes in population structure, it is of great significance to examine the characteristics of regional technological innovation gaps across different regions and periods in order to promote high-quality coordinated development. This paper analyzes data from 31 provinces in China collected between 2000 and 2020 to reveal the spatial and temporal evolution of the country's science and technology innovation gap. The impact of population structure on this gap is also examined through QAP analysis, including the effects of population ageing, human capital, population density, and population urbanization. The study found that:(1) There is a significant spatial imbalance in regional scientific and technological innovation in China, with a decreasing trend from east to west to central to northeast. (2) Urbanization to some extent widens the gap between regional scientific and technological innovation. Human capital and population density have a significant negative impact on the regional science and technology innovation gap. (3) From a spatio-temporal perspective, the negative impact of human capital on the regional technological innovation gap shows an increasing trend of fluctuation. Population urbanization has played a positive role in narrowing the regional innovation gap in science and technology. Finally, the effects of population density and population ageing on the regional science and technology innovation gap show heterogeneity in different periods. Population urbanization, human capital and population aging are the main factors affecting the regional technological innovation gap in the eastern, central and western regions, respectively.