Although major transportation infrastructure development plays a pivotal role in reshaping regional economic landscapes, its underlying mechanisms in influencing firms’ micro-level technology transaction behaviors remain unclear. Leveraging the construction of China’s high-speed rail (HSR) network as a quasi-natural experiment, this study investigates how HSR accessibility differentially shapes firms’ technology transfer patterns. Using patent transaction data from Chinese listed firms between 2000 and 2023, we find that HSR connectivity significantly promotes patent licensing—a relational form of technology transfer—while exhibiting no significant effect on patent assignment. This pattern suggests that HSR’s influence is most salient in contexts requiring sustained collaboration. We propose that the core mechanisms driving this result stem from HSR-induced spatial-temporal convergence: it mitigates ex ante information asymmetry regarding technological quality and reduces ex post coordination and monitoring costs during technology commercialization. Further analysis reveals that the effect of HSR is stronger among firms with low innovation reputation, limited market attention, and those in less competitive industries, indicating a substitutive relationship between HSR connectivity and formal market signals. Moreover, the promoting effect is more pronounced for firms characterized by low technological complexity, private ownership, and locations outside major innovation clusters, underscoring HSR’s distinctive role in facilitating tacit knowledge exchange and informal collaboration. By integrating transaction type heterogeneity and transaction cost perspectives, this study uncovers a novel pathway through which large-scale infrastructure shapes innovation diffusion, offering new theoretical and practical insights into how transportation revolutions empower technology markets.