The geographical distance between economic agents is an important factor affecting the efficiency of information transmission. The construction of transportation infrastructure can alleviate the information lost caused by geographical distance by reshaping the spatial structure. This paper uses the quasi-natural experiment of China's high-speed rail (HSR) opening to test the role of HSR on stock price synchronization, whether it’s information-content effect or governance effect. The study found that: (1) the introduction of HSR can reduce the stock price synchronization of companies along the railway, and the conclusions are still significant after controlling for endogenous problems by utilizing placebo test and instrumental variables approach. (2) mechanism analysis show that the opening of HSR reduces stock price synchronization through information-content effect rather than governance effect. (3) heterogeneity analysis find that when the information environment is weak or transportation resources are scarce, the impact of HSR opening on stock price synchronization is more significant. Our paper provides great inspiration for the crossover study of new economic geography and capital market accounting and finance, and confirms the positive role of infrastructure construction in improving the efficiency of capital market information, which affords references for achieving the interconnection of regional capital markets under the construction framework of “the Belt and Road”.