A new bridged silsesquioxane (BSQ) was synthesized with isophorone diisocyanate (IPDI) and 3-aminopropyltriethoxysilane (APTES). Highly cross-linked bridged polysilsesquioxane (BPSQ) sol was prepared by the sol-gel polycondensation of the as-synthesized BSQ under basic catalysis. Transparent film was obtained by dip-coating the BPSQ sol on the nickel sulfate hexhydrate (NSH, NiSO4綈2O) crystal wafer, an important kind of UV light filter used at wavelength 300 nm. The obtained BPSQ film was nonporous (pore volume is 2 נ10-3 cm3 g-1) and exhibited very high condensation degree of siloxane (99.0%). This film showed high optical transmittance and excellent moisture-resistant protection to the NSH filter. Moreover, the thermal stability of the NSH filter was also greatly improved by the as-prepared BPSQ film.