The invention belongs to the technical field of modified organic silicon resin preparation, and discloses a vinyl POSS (polyhedral oligomeric silsesquioxane) modified organic silicon resin with excellent optical and thermodynamic properties, and a preparation method and application thereof in the fields of LED (light-emitting diode) packaging materials, coating materials, optical lens materials and the like. The resin comprises the following components in parts by weight: 100 parts of POSS graft modified polysiloxane polymer, 20-80 parts of vinyl silicon oil and 0.0002-0.005 part of catalyst. The cage-type vinyl POSS used as a crosslinking agent and hydrogen-containing silicon oil are subjected to silicon-hydrogen addition to be successfully grafted into the organic silicon matrix so as to obtain the POSS graft modified polysiloxane polymer, and the POSS graft modified polysiloxane polymer is mixed and cured to obtain the curing product. The method overcomes the defect of material strength decrease caused by aggregation in the conventional POSS physical blending process. The vinyl POSS modified organic silicon resin can be used for preparing the transparent packaging adhesive with excellent optical and thermodynamic properties; and the light transmittance is up to 95% above, and the refractivity is up to 1.442.