To improve the high-temperature resistance and inhibit the secondary disasters (such as explosion/radiation leakage attributing to power failure or short circuit) after fire, polymer-based ceramifiable composites (PCCs) have grown significantly in fire protection field caused by strong self-supporting and water spraying ceramic layer at 600–1000 °C. Generally, PCCs are fabricated through incorporating fluxing agent, silicate fillers, synergist, flame retardant and so on into polymer matrix. The polymer matrix could provide the composites with good processability, the ability to ease shaping and high elasticity. In this review, the different PCCs are compared and the effects of polymer matrix on the ceramization mechanism of composites are discussed. The factors influencing the self-supporting strength and water-resistant spraying time of ceramifiable polymer-based composites such as the type and incorporation amount of silicate fillers, ceramization temperature and fluxing agent are discussed. Meanwhile, the influence of flame retardant on the flame retardancy and ceramization property of PCCs is analyzed. Some perspectives and future directions on how to highly generate flame-retarding and strong self-supporting ceramifiable composites are proposed.