The conventional polyurethane (PU) coatings have poor heat resistance, which will undergo severe pyrolysis when the temperature exceeds 200 °C. To overcome the shortcoming of conventional PU coatings, an ultraviolet (UV)-cured solvent-free hyperbranched polycarbosilane modified PU coatings was prepared by sulfhydryl-terminated polyurethane and allyl-terminated hyperbranched polycarbosilane. The initial decomposition temperature (Td5%) of the UV-cured coating ranges from 258 to 268 °C, which is obviously higher than those of the conventional PU coatings reported. The coating shows fairly low water absorption in the range of 0.6–1.36 wt% and exhibits grade 1, grade 2 and grade 3 adhesion to glass, tin plate and aluminum sheet, respectively.