Rhombohedral C₆₀ holds significant potential for applications in fields such as two-dimensional materials and catalysis; however, the synthesis of high-purity, high-quality rhombohedral C₆₀ remains challenging. In this study, rhombohedral C₆₀ was successfully synthesized at 6 GPa and 650 ℃. Characterization by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy and spherical aberration-corrected transmission electron microscopy confirmed the obtained sample as a high-purity two-dimensional rhombohedral structure. The effects of pressure and temperature (6-10 GPa, 650-800 ℃) on the polymerization of C₆₀ were investigated, clarifying the phase boundary between the rhombohedral phase and disordered amorphous carbon clusters. Temperature-dependent Raman spectroscopy revealed that the rhombohedral C₆₀ polymer remains stable up to approximately 350 °C, beyond which it depolymerizes, reverting to the pristine face-centered cubic C₆₀ molecules. This work defines a clear processing window for the synthesis of high-quality rhombohedral C₆₀ and establishes an experimental foundation for its further application in functional materials.