Most migrant workers in mainland China are officially covered by the New Rural Cooperative Medical System (NRCMS), a rural health insurance system that operates in their home communities. The NRCMS and the system of household registration (户口, hukou) are tightly linked and systemically interdependent institutions. Migrant workers have difficulties benefitting from this social protection because it remains spatially separated from them. Only a minority have access to urban health insurance systems. This paper sheds light on the institutional origins of the coverage problem of migrant workers and examines crucial policy initiatives that attempt to solve it. In the context of the ongoing hukou reforms, these policies aim to partially dissolve the systemic interdependence of hukou and health insurance. While the policies provide feasible, yet conflict-prone, solutions in short-distance and concentrated bilateral migration systems, covering migrants who cross provincial boundaries remains a challenge.