To address the issues of low mechanical strength，high volumetric shrinkage rate，and poor heat resistance encountered by low refractive index coatings in the cladding ofdouble-clad optical fibers during their use，and to enhance their performance in complex environments， a fluorine-modified polycaprolactone modifier was synthesized using trifluorooctyl alcohol，isophorone diisocyanate，and polycaprolactone triol. Additionally，a hyperbranched polyester-aluminum fluoride modifier was synthesized using hydroxylfluorinated aluminum nanoparticles and fluorine-terminated hyperbranched polyacrylates asmain raw materials. The structure and dispersion state of these modifiers were characterizedusing infrared spectroscopy，gel chromatography，and X-ray diffraction. The effects of the two modifiers on the mechanical strength，volumetric shrinkage rate，and heat resistance of low refractive index fiber coatings were investigated. The results indicated that both types of modifiers were successfully synthesized. The fluorine-modified polycaprolactone at a massfraction of 30% and the hyperbranched polyester-aluminum fluoride at a mass fraction of 4%， when added to the low refractive index coating，effectively enhanced the mechanical properties and heat resistance of the coating，reduced the volumetric shrinkage rate of the coating film， and improved the usage capability of double-clad optical fibers in complex environments.