Bismaleimide-triazine resin/barium titanate (BT/BaTiO(3)) nanocomposite films were prepared by mixing the nano-BaTiO(3) particles into BT resin, followed by films casting and thermal cure. The surface modification of BaTiO(3) nanoparticles with silane coupling agent results in excellent dispersion and enhances the interaction between BaTiO(3) and the BT matrix. The derived nanocomposite films exhibit improved dielectric constant, while the dielectric loss remains at a low level (<0.05). For the nanocomposite film containing 70 wt% of BaTiO(3), the effective dielectric constant at room temperature reaches 23.63, which is about 7 times larger than that of pure BT resin, and the dielectric loss is only 0.0212 at 100 Hz. The dielectric properties of the nanocomposite films are nearly frequency-independent, which is attributed to the excellent dispersion of BaTiO(3) nanoparticles in the BT matrix. The interaction between BaTiO(3) and BT affects not only the phase transition of BaTiO(3), but also the thermal behavior of BT. Moreover, the nanocomposite films exhibit improved thermal resistance. The highest glass transition temperature (T(g)) is 261 degrees C, indicating good reliability as dielectric materials in applications. (C) 2011 Elsevier B.V. All rights reserved.