At present, China's infrastructure investment projects along the Belt and Road routes show a steady upward trend, effectively consolidating the economic foundation of geopolitical cooperation under the Belt and Road Initiative, but they also suffer from the emerging sovereign debt default risks and problems. This paper constructs an evaluation system for the default risks of the countries along the Belt and Road. It is found that the per capita GDP, the fluctuation of economic growth, the inflation rate, and the debt ratio are the main factors that affect the default risks. The results showed that Israel, Brunei, Lithuania, Slovakia and Singapore had the lowest risk of default, while Yemen, Ukraine, Kyrgyzstan, Nepal, Bhutan and Moldova had the highest risk. Therefore, this study puts forward some suggestions to prevent and deal with the risks of debt default and enhance the sustainability of debt investment projects, including formulating differentiated investment strategies, introducing third-party market cooperation mechanism, and promoting the phased development of major infrastructure projects.