跨国铁路作为提升“一带一路”交通基础设施互联互通的关键载体，对构建跨国供应链，促进沿线国家经济发展具有重要作用。本文从运输时效、运输费用、运输稳定性三个维度对中国—中南半岛跨国铁路进行分析，揭示铁路沿线国家贸易关系的动态演进特征，并运用GTAP模型模拟预测铁路在部分联通、全线贯通及路网形成三个阶段的综合效应。研究发现：在运输时效和费用方面，中线中老泰铁路表现最佳，西线中缅印度洋新通道具备避开马六甲海峡直达印度洋的优势；运输稳定性上老泰段较东、西线更具优势，东线越南政治互信和民心相通不足；西线则受缅甸政局动荡影响显著。GTAP模拟结果表明，跨国铁路建设能够显著促进沿线国家GDP增长、社会福利提升、贸易条件改善，但对非沿线国家则具有正向和负向双重效应。铁路建设有助于老挝、越南和柬埔寨等国将产业发展重点从初级资源类产品转向加工制造业。研究对依托跨国铁路推动内外“双循环”和促进中国西部沿边开放具有重要意义。

Transnational railways are vital instruments for enhancing infrastructure connectivity under the Belt and Road Initiative, contributing significantly to cross-border supply chain integration and economic development in countries along the corridors. This study examines the China–Indochina Peninsula transnational railway from three dimensions—transport efficiency, cost, and reliability—highlighting the evolving trade relations among participating countries. Based on the GTAP model, it simulates the economic impacts of the railway in three stages: partial connectivity, full operation, and network integration. Results show that the central corridor (China–Laos–Thailand) demonstrates superior performance in transport time and cost. The western corridor (China–Myanmar–Indian Ocean) offers strategic value by bypassing the Strait of Malacca. In terms of stability, the Laos–Thailand section outperforms others, while the eastern line (Vietnam) is hindered by limited political trust and weak people-to-people ties, and the western line faces significant disruption due to Myanmar's political instability. GTAP simulations suggest that railway development enhances GDP, social welfare, and terms of trade in countries along the route, while producing mixed spillover effects on non-participating economies. Furthermore, it facilitates industrial upgrading in Laos, Vietnam, and Cambodia, enabling a shift from primary resource-based sectors toward processing and manufacturing industries. The study provides valuable policy implications for promoting the domestic–international dual circulation development pattern and advancing the opening-up of China's western border regions through transnational railway integration.