The present invention discloses an 8-methyl cage-shaped silsesquioxane resin with a structure as shown in the figure. The resin has the following characteristics that: 1) the structure of the synthesized resin can be controlled; 2) the resin is solid at the room temperature; the softening point is low; the resin can be dissolved in a plurality of common solvents; and the application is convenient; 3) the resin can do the solidification reaction with the influence of heat, irradiation, or even light to form a highly cross-linked polymer; and no small molecules are released in the solidification process; 4) the solidified resin has good mechanical properties, excellent chemical resistance and high heat resistance or heat-resistant oxidation, that is, the high temperature of thermal decomposition and the residual rate of thermal decomposition; 5) the resin has good dielectric properties and thermal insulation properties after solidification; 6) the resin can do the ceramic reaction; 7) the resin and the fiber have good bonding performances. The mechanical properties of composite material are good.