Composite quartz ceramics（SiO_2f/SiO₂） have excellent mechanical and dielectric properties and are widely used in radar radomes，but there are several hydrophilic groups and pores in the structure，which is easy to absorb water and moisture. In this paper，a kind of silicone coating with excellent waterproof and moisture-proof properties wasdeveloped. A variety of waterproof and moisture-proof coatings were prepared by usingTFTES，a low surface tension trifluoropropyl trimethoxy-silane（TFTES）containing —CF₃ as a hydrophobic modification agent，methyl or fluoromethylsilicane（JP or RU resin）as the coatingbody and OMMT as the filler. The results showed that after hydrophobic modification ofcomposite quartz ceramics，coated with OMMT/RU with 1. 5% of OMMT for 3 times，the water absorption of the sample was the lowest（0. 31%）. With OMMT/JP with 1% OMMT content coated 3 times，the moisture absorption of the sample was the lowest（0. 44%）.Considering the factors of thickness and mass increase，the sample coated with 3 OMMT_{1. 5}/RU₁₀₀ has the best hydrophobic moisture resistance and good dielectric properties.