The invention discloses a modified light-cured resin and a preparation method thereof. The modified light-cured resin composition is prepared from acrylic resin, epoxy resin, reactive diluent, radical initiator, kation initiator, polyhydric alcohols, flatting agent, flatting agent, wetting dispersant, half-cage type POSS, nanosilicon dioxide, and pigment. Compared with the prior art, the invention applies the half-cage type POSS to modify the light-cured resin; the POSS resin has excellent temperature resistance, and is able to effectively improve the vitrification transformation temperature of the resin system, and the aging resistance is good; moreover, the POSS can effectively fill gaps in the polymer, and reduce the contraction of the polymer. Meanwhile, the half-cage type POSS is in good compatibility with resin, and can completely dissolve in the epoxy resin, thus the dispersing problem during the resin preparation process is reduced. Therefore, the modified light-cured resin prepared by the invention is featured by high temperature resistance, high strength, aging resistance, and stable dimension.