With the strengthening of China's economic power and the further implementation of China's open-door policy, China's outward investment has increased year by year. Some international comments are only concerned about the former and there are some public opinions about China's outward investment threatening the host country's environmental quality. This paper takes the carbon emissions of 49 countries along the “Belt and Road” and the acceptance of China's outward FDI as samples, studies the impact of China's outward FDI on the carbon emissions of the relevant countries, and comes to the conclusion that: China's outward FDI is a major factor in China's economic development. It is concluded that China's OFDI increases the total carbon emissions of the countries along the Belt and Road while decreasing the carbon intensity, and the impact is carried out through the three major paths of economic scale, technological level and structural effect.