Anisotropic colloidal particles are important building blocks for the studies of self-assembly, which are visualized models for basic research and can be used to construct structured materials. Discs are one of the most typical anisotropic colloids; however, the synthesis of monodisperse colloidal discs with well-defined shape remains a challenge. Here we report a novel strategy for synthesizing polymeric discs based on frame-guided droplet shrinkage. This was realized by creating frame/liquid core/shell rings and utilizing the shrinking instability of the liquid rings. The resulting disc's shape parameters are tunable. The method is general, is not limited to specific polymers, solvents, and frames, and therefore has the potential to afford a variety of polymer discs. We also demonstrate the possibility of tuning the surface chemistry of the discs through surface-initiated polymerization. The frame-guided droplet shrinkage method opens up a new way to design and fabricate colloidal particles.