Housing is an important livelihood project. Guangzhou’s policy of converting non-residential housing to public rental housing has effectively increased the supply of public rental housing by revitalizing idle non-residential housing stock, alleviated the housing supply and demand contradiction, and provided housing security for new urban residents and young people. The study found that the “unchanged nature” renovation mechanism, the resolution of property rights conflicts, the innovation of multi-dimensional policy tools, and the strengthening of cross-departmental collaboration and supervision have provided replicable samples for housing security in megacities and super-large cities, as well as theoretical support and practical guidance for urban renewal and the optimization of housing security policies.