This article, using panel data of 264 cities in China (2005-2018), empirically analyzes the influence of National Innovation Demonstration Zone on urban innovation level and its spatial heterogeneity across difference-in-differences model. The research shows that the construction of National Innovation Demonstration Zone can significantly promote urban innovation level, but innovation effect is particularly significant in central and western cities and low-grade cities where innovation foundation is relatively weak. Finally, this article puts forward corresponding policy suggestions according to research conclusions to further improve urban innovation level.