Polymerization of fullerenes is an interesting topic that has been studied for almost three decades. A rich polymeric phase diagram of C₆₀ has been drawn under a variety of pressure P and temperature T conditions. Knowledge of the targeted preparation and structural control of fullerene polymers has become increasingly important because of their utility in producing novel fullerene-based architectures with unusual properties and potential applications. This paper focuses on the polymeric phases of fullerenes and their derivatives under high P and/or high T. First, the polymerization behavior and the various polymeric phases of C₆₀ and C₇₀ under such conditions are briefly reviewed. A summary of the polymerization process of intercalated fullerenes is then presented, and a synthetic strategy for novel structural and functional fullerene polymers is proposed. Finally, on the basis of the results of recent research, a proposal is made for further studies of endohedral fullerenes at high P.