Against the backdrop of the in-depth advancement of the Silk Road Economic Belt initiative, environmental protection in the overseas investment of Chinese enterprises has increasingly attracted the attention of the international community. From the perspective of international environmental law governance, this paper systematically examines the basic principles that should be established for the environmental legal system of the Silk Road Economic Belt. It points out that current international environmental governance is characterized by two parallel trends: unilateralism and cooperative governance. Environmental cooperation under the Silk Road Economic Belt should adhere to the principle of cooperation, which can be further specified into four subsidiary principles: the principle of identity based on sovereign equality, as the basic principle of identity; the principle of process centered on joint management; the principle of sustainable development as the objective; and the principle of fairness aimed at promoting the sharing of governance outcomes. These principles should not only reflect the political foundation of regional cooperation, but also embody the basic characteristics of environmental governance; they should not only conform to the general laws of global environmental governance, but also adapt to new trends in environmental cooperation in the new era. Through the establishment of the above principles, this paper aims to provide environmental legal guidance for the overseas investment of Chinese enterprises, promote the development of a green Silk Road Economic Belt, advance environmental justice and good governance in the region, and provide institutional support for the implementation of the 2030 Agenda for Sustainable Development.