Currently, global climate change governance has come to a critical moment. The climate funding is one of the key challenges in China’s high-quality construction of the “Belt and Road” and the “Green Belt and Road” under the dual-carbon target. This study quantitatively analyzes the climate funding needs of the Belt and Road Initiative (BRI)countries and evaluates the rationality of their funding needs based on the current status of climate investment acceptance and latest Nationally Determined Contribution (NDC) reports submitted by the 65 countries in BRI region. It is estimated that the total cumulative emission reduction of the countries in the BRI region by 2030 will be 91.48 Gt CO2-eq, and the ratio of mitigation and adaptation funds will be about 5:3. In addition, the results of the cost accounting model show that the average cost of carbon emission reduction in BRI countries is 74.75 USD/t CO2-eq, and the total financial demand of climate change is about USD 11.44 trillion. However, according to the UNEP standard of USD 40 per unit of reasonable emission reduction cost, the proper total financial needs of the BRI region should be USD 5.85 trillion. For high-quality construction of the “Belt and Road” and the development of international climate cooperation, the BRI countries should further improve their NDC reports and the rationality of climate funding needs. Then, they should form and implement the “Belt and Road” international cooperation strategy on climate change and promote partner countries to systematically carry out climate governance, so as to achieve the global temperature control target of 1.5℃/2℃ and contribute to the implementation of the Paris Climate Agreement and the global sustainable development goal of 2030.