In the context of globalization, common development has become an important goal pursued by all countries. This article aims to evaluate the impact of the “Belt and Road Initiative” (B&R) on the economic development of countries along the route, as economic cooperation between countries continues to strengthen and common prosperity becomes an increasingly important issue. This paper selects panel data from several relevant countries from 2004 to 2022 and uses the difference-in-differences method (DID) to compare the economic development between countries participating in the “B&R” Initiative and those that are not. The empirical results indicate the “B&R” Initiative has a promoting effect on the income per capita level and Industrial structure optimization of participating countries. Moreover, countries with a higher level of economic development are affected by the “B&R” Initiative, and their Income per capita growth effects are more obvious, while the increase in the proportion of secondary industry in less economically developed countries is more obvious. This paper finally puts forward relevant policy recommendations based on empirical results.