In this work, KTN-NH2/PI nanocomposites with high breakdown strength and low dielectric loss were obtained by modifying the KTa0.5Nb0.5O3 surface with 3-(2-aminoethylamino) propylmethyldimethoxysilane (APDS). Compared with KTN/PI, the loss tangent (tanδ) of KTN-NH2/PI was decreased. The breakdown strength (Eb) could reach to 242.12 kV/mm, which is about 1.49 times higher than that of KTN/PI. Based on the molecular dynamics simulation, the interaction between the modified KTN-NH2 and the PI matrix was higher than the KTN/PI, which would reduce the tanδ by restraining the dipole orientation polarizations. Moreover, the increase of hydrogen bonds improve the interfacial compatibility, which reduce the electric field distortion of organic-inorganic interface and improve Eb.