Silicones contain only carbon, hydrogen, oxygen and silicon, so they decompose to produce water, carbon dioxide and silicon dioxide during combustion. Silica produced in the combustion process of silicone resin can be evenly covered on the surface of the fuel to form a hard shell layer, to prevent the melting of the fuel dripping effect; At the same time, the silica is also a diffusion shielding layer, which can prevent the vaporized organic matter produced by thermal decomposition of the internal polymer material at high temperature from diffusing to the combustion zone. Silica shell has low thermal conductivity and good thermal insulation effect, which can block heat transfer during combustion. The flame retardant effect of silica hard shell produced in the combustion process of silicone resin can be realized by a variety of effects, which is based on the mechanism of condensed state flame retardant.