Abstract: As social infrastructures,digital platforms have become deeply embedded in global social practices and the organization of social relations,giving rise to platform institutions that shape the mediated practices of the public.Unlike traditional institutions grounded in collectively formed social consciousness,platform institutions are company-governed frameworks of social action that tend to prioritize platform interests over public value.Through demand-side network lock-in,supply-side data barriers,and governance-side black-box opacity,private power embedded in platform institutions gradually produces institutional lock-in.In this process,the encroachment of platform private power on public value is no longer primarily a question of normative justification;rather,it accumulates through institutional inertia and path dependence.Moreover,by relying on code as law and technical opacity,platform institutions can bypass conventional legal oversight,exclude governments and the public from rule-making,and secure formal legality while obscuring questions of substantive legitimacy.Addressing the governance dilemmas of global platform institutions therefore requires a shift from private-power competition to public-value-oriented competition.This shift depends not only on user-driven platform nomadism and reverse-engineering practices,but also on promoting the two-way global circulation of Chinese platforms to disrupt the monopolistic structure of the existing platform ecosystem.