Novel covalently bonded nanoscale mesoporous silica (NMS)/polyimide (ODPA-BAPP) nanocomposites were synthesized through the bridge 3-aminopropyltrimethoxysilane. Abundant reactive amino functional groups inside the mesopore channels of NMS can interconnect with numerous polyimide main chains, forming multilinked and complex NMS/PI networks. These multilinkages, NMS inherent nanoporosity, and the uniform dispersion of NMS in polyimide significantly improve thermal stability, mechanical properties, elongation, moisture absorption, and dielectric constant of these novel materials over those of neat polyimide. For instance, the storage modulus is increased by 160%, the decomposition temperature by 35.7 degrees C, and the glass transition temperature by 14.5 degrees C. The maximum elongation increases by 66%, hardly observed in other polyimide nanocomposites, probably because the covalent bond and NMS nanopore can absorb more energy than pristine poyimide before failure. The nanoporosity of the core of the NH2-NMS material within the nanocomposite film is most likely responsible for the decrease of dielectric constant by 10%.