The Belt and Road Initiative (BRI) is a development plan proposed by China that aims to build a new platform for international cooperation and create new drivers of shared development. South Asia is a key area in the Belt and Road Initiative, including eight countries. As the BRI implemented, China’s trade with South Asia has been gradually strengthened. This paper explores the influencing factors of China-South Asia trade under the background of the BRI by using Gravity Model of Trade. The results show that economic growth in China and South Asia, increase of savings rate and improvement of industrialization in South Asia has a significant positive effect on China-South Asia trade. While the development gap between China and South Asia has negative effect on China-South Asia trade.