Abstract: Common prosperity is the essential requirement of socialism with Chinese characteristics and the core goal of Chinese-style modernization. Based on panel data from 11 provinces and cities in the Yangtze River Economic Belt from 2011 to 2020, we empirically examine the impact effect, transmission path, and non-linear characteristics of digital infrastructure on common prosperity. The study shows: first, digital infrastructure significantly promotes common prosperity, and this conclusion remains valid after a series of robustness tests; second, regional heterogeneity analysis indicates that the promotion effect is strongest in the midstream regions, followed by the downstream regions, and not significant in the upstream regions; third, digital infrastructure can indirectly promote common prosperity by enhancing fiscal support; fourth, the impact of digital infrastructure on common prosperity exhibits a single-threshold effect, with the promotion effect weakening after crossing the threshold. Finally, the paper provides policy recommendations in aspects such as policy optimization, regional coordination, fiscal support, and dynamic monitoring.