Innovation is increasingly important in enhancing local competitive advantage and reshaping the global economic pattern. The rapid rise of the digital economy provides strong support for innovation development. This paper uses panel data of cities and micro-patent data in China, analyzing the impact and mechanism of digital infrastructure construction on urban innovation based on the perspective of the technology division. It is found that the construction of digital infrastructure can significantly promote the quantity of urban innovation and the effect is characterized by an increasing marginal payoff. The technology division of labor is an important transmission channel for digital infrastructure construction to affect urban innovation. The construction of digital infrastructure will also promote the improvement of urban innovation quality and can play a role in narrowing the innovation development gap between regions in the long term. Digital China and national innovation system construction policies, represented by “Broadband China” and innovative city construction, can create a policy collaboration effect with digital infrastructure construction to help the development of urban innovation jointly. The research in this paper broadens the mechanism analysis of digital trends affecting urban development and provides ideas for promoting urban innovation.