This paper studies the mechanism of how urban infrastructure affects urban economic growth through FDI by theoretical and econometric analysis, based on overall and structural preferences of FDI for urban infrastructure stock in the three metropolitan belts along the eastern coast of China, the Bohai Rim, the Yangtze River Delta and South China. It is found that: (1) Whether FDI has a preference or structural preference for the overall stock of urban infrastructure depends on whether the corresponding stock of infrastructure crosses the minimum threshold and the “saturation” threshold of FDI’s preference for infrastructure;(2) FDI has a preference for urban infrastructure, but there is not necessarily a mechanism for infrastructure to promote urban economic growth by attracting FDI, which is influenced by whether there are factors that can stimulate the positive spillover of FDI on economic growth;(3) Urban infrastructure moderates the impact of FDI on urban economic growth depends not only on the growth effect of FDI, but also on the impact of infrastructure improvement on the allocation efficiency of factor resources in FDI investment areas. The conclusion of the study has important theoretical reference and decision-making reference for China’s current policy practice of improving the level of opening up in an all-round way.