Abstract: By making use of the urban panel data and detailing the indexes of industrial development and urban expansion, this paper examines the action mechanism of industrial development and urban expansion on the level of urban innovation. The results of the empirical research show that the impact of industrial structure upgrading on the level of urban innovation is not significant, and that industrial clustering, urban population expansion and urban area expansion can all promote urban innovation. Further study shows that industrial development and urban expansion have a significant threshold effect on the level of urban innovation. When the degree of city-industry integration is low, the upgrading of industrial structure, industrial clustering and urban area expansion can all significantly inhibit the improvement of urban innovation. However, when the degree of integration reached a certain level, the promotion effect of the three factors on the level of urban innovation is gradually highlighted. With the improvement of the integration degree, the promotion effect of industrial clustering, urban population expansion and urban area expansion on urban innovation is also gradually increasing.

Key words: industrial development; urban expansion; urban innovation; city-industry integration