The invention relates to sulfur-containing benzophenone modified hyperbranched self-initiation light-curable resin and a preparation method thereof. The self-initiation UV resin provided by the invention takes TMP as a core, has a hyperbranched three-dimensional structure, and contains a plurality of functional active groups, a plurality of sulfur-containing benzophenone photo-initiation groups and a plurality of branched chain bulk alkane groups. The resin has pigment bearing performance, high solid content, low viscosity and storage stability. The self-initiation efficiency is high, and the defects of low curing rate, easy yellowing of a coating, surface migration, strong volatility, large heat loss, generation of harmful substances and pungent smell and the like of an additional BP initiator are overcome. The sulfur-containing benzophenone hyperbranched self-initiation light-curable resin prepared by the invention has excellent flexibility, adhesive force, chemical resistance, heat resistance, aging resistance, oil resistance, wear resistance, pollution resistance and impact strength, is odorless in coating, and can be used for UV colored floor coatings, UV wood coatings, UV alloy coatings, UV circuit board ink, UV plastic coatings and the like.