Abstract: To enhance the Chengdu-Chongqing economic circle’s construction and foster high-quality economic growth, the pivotal contribution of the digital economy is underscored. Utilizing data from 139 counties (districts) within the Chengdu-Chongqing area from 2009 to 2019, this study employs an advanced difference-in-differences approach to examine the effect and mechanisms through which the establishment of “Broadband China” demonstration cities influences the innovation levels of county-level cities. The findings indicate that the “Broadband China” strategy, aimed at bolstering information infrastructure, has notably elevated the innovation levels in the Chengdu-Chongqing region, a result consistently upheld through various robustness tests. Further investigation shows that, owing to distinct county characteristics such as economic bases, geographical positions, and resource allocations, the policy impacts are more pronounced in the central zones of the Chengdu-Chongqing dual-city area and its urban sub-districts. The study also highlights that in this region, the development of information infrastructure chiefly boosts city innovation levels indirectly by enhancing local informatization and fostering the concentration of productive service sectors. Consequently, there’s a call for the augmented construction and strategic layout of next-generation information infrastructures to bolster county-level cities’ innovation capacities, thereby propelling the high-quality development of the Chengdu-Chongqing economic circle.