This paper examines the impact of geographic location and high-speed rail (HSR) launch on the capital market efficiency in terms of cash dividend payouts. A firm's geographic location reflects the degree of information asymmetry, and HSR launch improves information dissemination. Using a sample of China's public firms, we find that the launch of HSR significantly reduces the cash dividends in firms located in neighboring cities along the HSR line. This effect is more pronounced in firms experiencing agency issues, especially those operating in complex businesses, audited by small auditors, state-owned enterprises, and those characterized by greater free cash flow and fewer investment prospects. Further analysis shows that the suppression of cash dividends accompanied by the launch of HSR only exists before implementing the mandatory dividend policy. The results indicate that the launch of HSR alleviates information asymmetry between external investors and managers, reduces agency costs, and improves stock market efficiency.