A nano-silica hybrid vinyl phenyl silicon intermediate, a preparation method therefor and a use thereof in an environmentally-friendly insulating varnish are provided. The nano-silica particles are dispersed uniformly and stably; the nana-silica hybrid vinyl phenyl silicon intermediate has the advantages of resisting high temperatures and coronas and being high in activity; the temperature index measured according to a secant method is 200° C.-240° C., the measured corona-resistant time is 18-36h, and the vinyl active sites carried thereon can have a good compatibility with polyesterimide, heat-resistant polyesters, hydrogen-containing siloxane and modified epoxy; the intermediate is particularly suitable for preparing a high-temperature-resistant and corona-resistant solvent-free insulating varnish; and there are on volatile gases during use, thereby causing on pollution to the atmospheric environment.