It is particularly important for promoting coordinated regional development whether infrastructure construction can optimise resource allocation and reshape the spatial distribution of innovation factors. Using the opening of high-speed rail and the "Broadband China" demonstration city as quasi-natural experiments for transport and information infrastructure construction respectively, the impact of infrastructure construction on city innovation from a heterogeneous infrastructure perspective by the data of 284 cities in China from 2004 to 2020 was explored. The results are as follows. The opening of high-speed rail can effectively exert the effect of human capital and financial support to promote urban innovation, and this promotion is more significant in the central and western cities and northern cities, which is conducive to promoting regional coordinated development. The demonstration city of "Broadband China" has an important role to promote the innovation level of eastern and southern cities, and promotes the unbalanced development of regions. Further analysis shows that there is a superimposed effect on the promotion of urban innovation by transportation and information infrastructure construction. The demonstration city of "Broadband China" can effectively exert the effect of human capital and financial support by the power of "high-speed rail", thus accelerating the innovation development of cities in the east and south, and further expanding the regional unbalanced development. The research findings contribute to understanding the complex innovation effects of transport and information infrastructure construction, and have important implications for the spatial layout of infrastructure, the optimization of innovation spatial pattern and the region coordinated development.