Abstract: Using glass frits can improve mechanical strength and keep structure integrity of ceramifiable silicone rubber matrix composites after pyrolysis at high temperature. In order to study the effects of composition of glass frits on the high-temperature resistance properties of muscovite/silicone rubber composites, two composites were prepared by using glass frits A and B as fluxing agent, respectively. The mechanical properties, microstructure, thermal decomposition properties and ceramic mechanism of both composites were studied. The results show that tensile strength of muscovite/silicone rubber composites is 3~4 MPa at room temperature, and flexural strength of the samples after pyrolysis is 0.3-4.5 MPa and can keep structure integrity at 600-1 200℃. SEM results reveal that glass frit B is helpful to form a large amount of liquid phase structure, and improve the strength and structure of ceramic layer produced after pyrolysis. TG results show that glass frits can accelerate the decomposition of silicone rubber, so the amount of glass frits should be controlled. XRD results show that adding glass frit B which includes more SiO₂ and K₂O to muscovite/silicone rubber composites can form an amorphous phase and a potassium aluminum silicate (K₂O·Al₂O₃·6SiO₂) during the temperature change and therefore increase the strength of ceramic layer.