Abstract: With ‘the Belt and Road’ Initiative, the consensus among the countries has been achieved to promote low-carbon development. Based on the panel data of ‘the Belt and Road’ Countries during 1997-2018, this paper explores the impacts of Foreign Direct Investment (FDI) on carbon emissions by stepwise regression, heterogeneity analysis and threshold regression. The results show that: (1) FDI to ‘the Belt and Road’ Countries has significantly increased carbon emissions, indicating the ‘pollution haven’ effect. (2) ‘The Belt and Road’ Initiative proposed by China in 2013 focuses on green development, which helps to weaken the ‘pollution haven’ effect of FDI on carbon emissions in ‘the Belt and Road’ Countries. It reflects China's leading role in global environmental governance, especially in climate change response. (3) Economic development can weaken the ‘pollution haven’ effect of FDI on carbon emissions, but rapid economic development, especially industrial growth, significantly increases carbon emissions. (4) Policy, innovation and development mechanisms all lead to significant changes in the carbon emission effect of FDI, among which the development mechanism has the greatest influence, while the innovation mechanism is the most effective. (5) Strengthening environmental regulations promotes the ‘pollution halo’ effect of FDI. ‘The Belt and Road’ Initiative plays an important role in strengthening environmental regulation in ‘the Belt and Road’ Countries. Therefore, in order to promote the ‘pollution halo’ effect of FDI, the green ‘Belt and Road’ initiative should be reinforced and the low-carbon investments from China or other environmentally responsible FDI should be introduced. It is also necessary to strengthen the innovation in low-carbon science and technologies. With the technological improvement, policies, innovation and development mechanisms can be coordinated to guide FDIs into green and low-carbon fields. In addition, a combination of environmental access mechanisms and environmental economic instruments should be used to achieve high-quality development.