Abstract: The construction of new western land-sea corridors plays an important role in the coordinated development of China's regions, and one of its important goal is providing strong support for the high-quality economic development of the western region and integration into the new development pattern. Based on provincial panel data from 1995 to 2020, this paper uses the double difference method to empirically test and finds: The economic catch-up effect of the new corridor construction has regional differences, significantly contributing to the economic catch-up speed of Chongqing, Guangxi and Guizhou, which were the first to participate in the new corridor construction; the “counterfactual” test based on the synthetic control method shows that the positive contribution of the new corridor construction to the economic catch-up speed of Guizhou is the largest, followed by Chongqing, and the positive contribution to Guangxi is the smallest, and there are significant time differences in the contribution to these three provinces, but the economic catch-up effect of the new corridor construction does not show persistence. Based on these findings, this paper suggests that in order to strengthen the coordinated regional development role of the new corridor construction, it is necessary to further release its long-term economic catch-up effect and avoid falling into the “policy trap”.