Abstract: Transportation infrastructure has an important effect on the innovation activities of micro-units by accelerating the cross-regional flow of human resources and other innovation factors. Taking the data of Chinese manufacturing A-share listed companies as samples, this paper conducts an empirical analysis with the difference-in-differences method. The findings show that the opening to traffic of high-speed rail has significantly promoted the quality of patents of the enterprises along the line, and that the conclusion is still robust after controlling the endogeneity. The mechanism analyses show that the impact of high-speed rail on corporate patent quality is realized through knowledge diffusion effect, resource allocation effect and cooperative innovation effect. The findings of further study show that the quality improvement of high-speed rail patents has significant spatial heterogeneity and industrial heterogeneity. The high-speed rail has a more obvious effect on the patent quality of the enterprises located in regional central cities, while the impact on the enterprises located in peripheral cities depends on their geographical distance to the central cities. Compared with the low-and medium-tech industries, high-speed rail has a more significant innovation-promoting effect on the enterprises in high-tech industries.

Key words: high-speed rail, patent quality, difference-in-differences method, spatial heterogeneity