Phenyl modified MTQ silicone resins structurally consisted of momofunctional siloxyl group (M segment), trifunctional siloxyl group (T segment) and tetrafunctional siloxyl group (Q segment) with different molecular weight, different phenyl group contents and different segment ratios (M∶T∶Q) were synthesized by cohydrolysis-condensation method initiating from hexamethyldisiloxane, 1,1,3,3-tetramethyl-1,3-divinyl disiloxane, phenyltrimethoxysilane and tetraethoxysilane. The efractive index (RI) of MTQ increased with the increase of Ph/R value and it reached up 1.5117 when Ph/R value was 0.39. MTQ silicone resins were characterized by FT IR, 1H-NMR and GPC spectra, and M∶T∶Q ratio was calculated based on the quantitative analysis of 1H-NMR spectra. Thermal stabilities of MTQ resins in inert atmosphere were studied by TGA, DTG and TGA-IR spectra. The structure of the remnants collected after high temperature treatment was analyzed by XRD and FT-IR. The results indicate that the degradation of MTQ is consisted of three stages, and their thermal stabilities enhance with the increase of phenyl content. After calcinated under higher temperature, MTQ resins are completely transformed into amorphous SiO2.