The research presents methodological tools for assessing the management of working capital as the basis for leading the eco-efficiency use in the system development of the green economy of Russia and Belarus in the context of foreign trade and mutually beneficial cooperation. The authors developed a dynamic model of the working capital management’s green economy, according to the criteria of turnover growth. The developed model corresponds to the expansion of the green economy declared by the state programs of Russia and Belarus. The process of developing a green economy in the economic space of the textile industry enterprise “Mogotex” JSC is presented from the standpoint of optimizing the interaction strategy in the system of the enterprise’s sustainable development. The sustainable development of Russia and Belarus’s regions is largely determined by foreign economic relations that ensure eco-efficient production in regions with a vector of inclusiveness, intersectorality, innovation, resource conservation, industrial symbiosis, and competitiveness growth. The relevance of modeling international cooperation and responsibility is justified by mutually beneficial international cooperation in the system of sustainable growth of national economies.