As a new form of regional multilateralism, the Belt and Road Initiative is China’s most significant strategic move for external engagement in international economic law, following its World Trade Organization accession. This paper analyses China’s approach towards the Belt and Road Initiative from a legal perspective, focusing on three questions: first, what is the proper scope of the Belt and Road Initiative? Second, is there an identifiable approach that China adopts in the Belt and Road Initiative context, and, if so, what is its key legal characteristic? Third, is China’s Belt and Road Initiative approach sustainable? Employing a functional approach in defining the Belt and Road Initiative, the article identifies three qualities to China’s approach to the Belt and Road Initiative: (i) that it is a hub-and-spoke network, (ii) it adopts a three-track institutional and mechanism approach, and (iii) a dual- track normative approach. Compared with the US trade approach (particularly the US–Mexico–Canada Agreement), these qualities reveal the key characteristic underpinning China’s Belt and Road Initiative approach: maximised flexibility regarding institutions and norms to address uncertainties and challenges in the Belt and Road Initiative. Such flexibility will likely assist in ensuring that China’s Belt and Road Initiative approach is sustainable by enabling trial-and-error, if properly managed. However, it also gives rise to concerns around China’s Belt and Road Initiative approach, especially as to its predictability, coherence, and transparency.