In order to prepare coatings with excellent moisture-proof performance, organic-bridged silane precursor 3-trimethonylsilylpropyl-2-methyl-3-[(3-trimethonylsilyl)propylsulfanyl]propionate (MPMA) were prepared by mercaptopropyl trimethoxy silane (MPTMS) and 3-(methylacrylloxy)-propyl trimethoxy silane (MATMS) via thiol-ene click reaction. The MPMA sol was obtained by hydrolyzation and condensation polymerization under acidic conditions through sol-gel method. Then the organic-bridged polysilsesquioxane coating were fabricated by depositing MPMA sol on glass slide through dip-coating method and on polyetherimide (PEI) through coating method, respectively. The moisture-proof performance of the coating was explored by measuring the water vapor transport rate (WVTR) and the effect of aging time on the moisture-proof performance of coatings was investigated. The results showed that the WVTR of coatings was as low as 3.13 g·m-2·d-1 when the sol aging time was 30 h, indicating that the coating possessed excellent moisture-proof property. Besides, the coating performed good optical transmittance, level 0 in adhesion evaluation test and 3H pencil hardness.