As a special kind of organosilicon products, phenyl organosilicon products have more excellent performance than methyl organosilicon products, excellent high and low temperature resistance, radiation resistance and aging resistance, which make it widely used in high-end fields and extreme occasions. The synthesis process and application formula of phenyl organosilicon products are quite different from that of methyl organosilicon products, which can not be mechanically copied. It is necessary to form its own synthesis and application system, establish various models, and provide convenience for product design. There are many kinds of phenyl organosilicon products, which are widely used. Different industries have different requirements and standards for the application of products. In order to better meet the needs of the market and customers, subdividing the application market has become the key and hot spot for organosilicon researchers, which is also an urgent problem to be solved. This thesis is devoted to the study of the synthesis and application performance of phenylpolysiloxane products, focusing on the modeling of the influence of phenyl content and molecular structure on the refractive index of phenylpolysiloxane, the preparation of high-performance transparent phenyl silica gel, and the preparation of low permeability transparent phenyl encapsulated silica gel. The specific work is as follows: (1) the molecular structure design and synthesis research of phenylpolysiloxane Research. High purity octaphenylcyclotetrasiloxane was prepared by using Diphenyldimethoxysilane as raw material. Using acetone as solvent, Diphenyldimethoxysilane was completely dissolved in it, while octaphenylcyclotetrasiloxane was slightly dissolved, and the octaphenylcyclotetrasiloxane was rapidly crystallized and precipitated. The yield of the product is high, and the content of octaphenylcyclotetrasiloxane reaches 99.7%. The octaphenylcyclotetrasiloxane containing polychlorinated biphenyls is dissolved in toluene, adsorbed and filtered by diatomite, n-heptane is added into the filtrate, octaphenylcyclotetrasiloxane is crystallized and separated from the mixed solvent by recrystallization, and then the crystallized octaphenylcyclotetrasiloxane is separated