This study selects 61 countries along with the “Belt and Road Initiative” (BRI) as a sample. Under the framework of network analysis, we first describes the (weighted) average degree, network density, average agglomeration coefficient and average path length of export trade network, portfolio investment network, equity and fund investment share network and bond investment network of sample countries from 2001 to 2019, and reveals the common “small world” characteristics of the four networks; and then uses the cross-sectional expornalrandom graph model (ERGM) and temporal ERGM to consistently confirmed that the portfolio investment network, equity and investment fund network, and bond investment networks are conducive to the development of the export trade network of countries across the BRI countries during the sample period and it is found that the bond investment network plays the most important role in the development of export network among them;what’s more, the more significant of attribute characteristics of the countries, such as investment liberalization and financial liberalization, the more easy to establish the closer export trade relationship across the BRI; Countries with larger economies and populations are more active in export trade networks. Finally, the paper further points out the policy implications of the above conclusions.