The present study adopts a new political intervention analysis approach to evaluate the impact of the "21 st Century Maritime Silk Road" (MSR) policy. The basic concept is to investigate dependence amongst cross-sectional units to construct counterfactuals without intervention. Thus, the effect of policy intervention is simply the difference between the outcomes with and without intervention. The panel data of 14 countries along MSR are used to illustrate the methodology. Real data analysis shows that the MSR policy exerts a positive effect on the trade of China and Southeast Asian countries. Furthermore, policy implications are provided based on the analysis.