Abstract: The poor heat resistance of silicone rubber seriously restricts its application in the field of high temperature resistance. To solve this problem, low melting oxide Sb₂O₃ and Bi₂O₃ were used as fluxing agent to study the effects on the ceramizable properties of diatomite/silicone rubber composites. The thermal stability of Sb₂O₃ and Bi₂O₃ on diatomite/silicone rubber composites was analyzed by TG, the bending strength after pyrolysis was tested by universal mechanical testing apparatus, field emission scanning electron microscope (FESEM) and energy dispersive spectrometer (EDS) were used to analyze the microstructure and composition of the pyrolysis products, and ceramic mechanism was studied by XRD. The results show that metal oxide of Sb₂O₃ and Bi₂O₃ can accelerate the decomposition of silicone rubber, but they can obviously improve the bending strength of the specimen after pyrolysis. Bi₂O₃ and Sb₂O₃ are contribute to the formation of a continuous bridge structure in the process of composites pyrolysis by FESEM. Through EDS analysis, eutectic phenomenon may be occurring between SiO₂ and Sb₂O₃, Bi₂O₃ and SiO₂ in the process of composites pyrolysis and help to form a ceramic structure. XRD show that the amorphous phase structure is formed after the addition of fluxing agent to diatomite/silicone rubber composite, which can improve the strength of the ceramics.