Based on the macro data of the countries along the "Belt and Road" from 2009 to 2020， which are the intended founding members of the Asian investment bank，this paper studies the impact of financial development on the export technological complexity of the countries along the " Belt and Road" areas. The research finds that the effect of financial development on export technological complexity is significant. Firstly， the scale of domestic financial development significantly promoted the level of export technological complexity of the country. Furthermore， Foreign development assistance hindered the progress of export technological complexity in short and medium term， but its long-term effect effectively increased the level of export technological complexity. Further research finds that financial development can promote the improvement of local export technological complexity by acting on infrastructure.