Urethane-acrylate prepolymers for secondary coating of optical fiber were prepared from the 2,4-tolylene diisocyanate (TDI), poly(tetramethylene oxide)glycol (PTMG), hexane diol (HD), and 2-hydroxyethyl acrylate (HEA) with dibutyltin dilaurate as a catalyst. Five types of reactive diluents having mono-, di-, and trifunctionality-trimethylol propane triacrylate (TMPTA), phenoxy ethyl acrylate (PEA), hexanediol diacrylate (HDDA), tripropyleneglycol diacrylate (TPGDA), and isobornyl acrylate (IBOA)-were used in this study. Ultraviolet (UV)-curable coating materials were formulated from the prepolymer, five different diluents, and 1-hydroxy cyclohexyl phenyl ketone (Irgacure 184) as a photoinitiator. In this work, the effects of various diluents on mechanical and dynamic mechanical properties of UV-cured films were studied. The structure and properties of the films obtained from the UV photopolymerization of urethane-acrylate prepolymer were investigated by FT-IR spectroscopy, dynamic mechanical measurement, refractive index measurement, and tensile testing.