Information infrastructure connects various subjects in economic and social development, overcomes regional obstacles to a certain extent, and reduces the differences between urban and rural economic factors. With a 2005—2019 national sample of 260 prefecture-level cities and municipalities directly under the central government, the impact of information infrastructure on urban-rural income gap is investigated through bidirectional fixed effects model and the threshold model. The study found that: the impact of the information infrastructure scale on the income gap between urban and rural areas presents an "inverted U shape" nonlinear relationship—an increasing before declining trend. At present, most cities in China have crossed the inflection point and entered the stage of narrowing the income gap. There is a single threshold for information infrastructure, and double thresholds for economic development and education level; the impacts of information infrastructure in different threshold ranges on urban-rural income gap are different. The information infrastructure has different effects on the income level of urban and rural residents, showing a linear positive correlation for urban residents and a "U-shaped" nonlinear relationship for rural residents. The research results are basically sound, and targeted policy suggestions are put forward according to the conclusions.