Strengthening the value chain cooperation among developing countries becomes an effective way for developing countries to resolve the crisis of anti-globalization and get rid of the lock at the lower end of the value chain. The Belt and Road initiative provides a new direction for developing countries to promote the value chain cooperation among them. However, as an open cooperation platform, the Belt and Road initiative does not provide a menu-style solution. We think that the establishment of a deeply integrated free trade agreement（FTA）network among the Belt and Road countries is one path to strengthen value chain cooperation under the framework of this initiative. So, does the available empirical datum support this idea? The answer to this question can provide policy reference for China and the Belt and Road countries to construct high-standard FTAs as a starting point to carry out value chain cooperation effectively.

This paper firstly illustrates the influence mechanism of FTA depth in promoting regional value chain cooperation. With the data of 64 Belt and Road countries from 2000 to 2015, this paper then empirically identifies the actual influence, mechanism and differentiation characteristics of FTA depth on regional value chain cooperation. It further examines whether the depth of FTAs affects the value chain cooperation between state parties and other countries. The main conclusions of this paper are as follows: Firstly, the improvement of FTA depth is conducive to the value chain cooperation among the Belt and Road countries, and this conclusion is still valid for the robustness test from multiple perspectives. Secondly, the deepening of FTAs can promote regional value chain cooperation by reducing trade costs and promoting direct investment, and the reduction of trade costs is the more important transmission channel. Thirdly, the increased depth of FTAs on non-tariff topics and“WTO-X”topics have a stronger effect on promoting the value chain cooperation among the Belt and Road countries, and the promoting effect is stronger for the countries with a high degree of initial regional value chain cooperation, and small geographical and cultural differences. Fourthly, while promoting the value added of state parties to flow out of the region, the deepening of FTAs will not inhibit the regional value chain cooperation between state parties and non-state parties.

Our major contributions are as follows: Firstly, this paper analyzes the determinants of value chain cooperation among the Belt and Road countries from the perspective of FTAs, and expands the research perspective of existing literature. Secondly, this paper reveals that the deepening of FTA depth could promote the value chain cooperation among countries by reducing trade costs and promoting direct investment. Thirdly, this paper confirms that the deepening of FTAs among the Belt and Road countries has a certain inclusive effect on promoting value chain cooperation.