Enhancing transport infrastructure connectivity is the key to promoting high?quality Belt and Road construction. Based on the panel data of 51 countries along the Belt and Road from 2011 to 2019，a fixed?effect model was established to empirically test the impact of different types of transport infrastructure quality of host countries on China’s export and import respectively. The results show that the quality of different types of transport infrastructure in the host country have a greater promoting effect on China’s import than its export. From the perspective of China’s export to the host country，the port infrastructure quality has the strongest effect on China’s export，followed by the highway and aviation infrastructure quality，while the railway infrastructure quality has no significant effect. From the perspective of China’s import from the host country，the quality of highway infrastructure has the largest promoting effect on China’s import，followed by the quality of port infrastructure，while the quality of railway and aviation infrastructure has little influence. Through the mediation effect test，it is found that the transport infrastructure quality of the host country will promote the growth of China’s import and export trade by reducing trade costs. The interaction term analysis found that the improvement of road and rail infrastructure in the host country has a positive spillover effect on port and aviation infrastructure and port infrastructure improvement on aviation infrastructure trade promotion，while the improvement of road infrastructure has a negative spillover effect on railway infrastructure trade promotion.