Abstract: In this paper, poly centric agglomeration index of each province is constructed based on Landscan data, and the impact of polycentric agglomeration on urban innovation and the mechanism of action were investigated by using instrumental variable estimation. The results show that, on the whole, urban innovation presents a significant inverted u-shaped change trend with the increase of poly centric agglomeration. Meanwhile, there are several regions in China where urban innovation is inhibited by excessive polycentric agglomeration. According to the sub-sample test, the inverted u-shaped impact of polycentric agglomeration on urban innovation is mainly reflected in large cities and inland areas, while the innovation of small and medium-sized cities and coastal areas can significantly benefit from the development of polycentric agglomeration. In addition, market integration and the factor flow are important ways for polycentric agglomeration to affect urban innovation. Further research shows that the effect of polycentric agglomeration on urban innovation is affected by urban distance and infrastructure.

Key words: polycentric agglomeration, urban innovation, mediation effect, regulatory effect