To improve the stability of WBFs at high temperatures, a novel organosilicon polymer (CBV) was prepared by surfactant-free emulsion polymerization in this work. The incorporation of siloxane groups into the CBV molecular structure enables its chemical adsorption onto clay mineral surfaces through the formation of Si–O–Si covalent bonds, significantly enhancing its adsorption stability at high temperatures. Fourier transform infrared spectroscopy and thermogravimetric analysis confirmed the expected molecular structure and excellent thermal stability of CBV. With the addition of 3.0% CBV, the fluid loss of the drilling fluid was reduced to 20 ml under 180 °C, and its rheological properties and inhibition performance were also improved. Based on the original work, we conducted a comparison of the adsorption performance of organosilicon polymers with commonly used inhibitors and further studied the adsorption performance and mechanism of organosilicon polymers in WBFs under high-temperature conditions. The adsorption experiment found that the chemical adsorption with clay makes it difficult for CBV to desorb at high temperatures. Compared to the physical adsorption mechanism of traditional additives, CBV has achieved a transformation of adsorption from physical adsorption to chemical adsorption, providing a new approach to solving the problem of high-temperature instability in drilling fluids. In addition, soap-free lotion polymerization avoids the use of organic solvents, endows the product with unique film-forming hydrophobic characteristics, and further enhances its adsorption and film-forming effects on the shale wall.