Abstract: We investigated the application of nonlinear composite insulating materials which were constructed by using the principle of dielectrophoresis in the optimization of the local electric field of IGBT. First, silicon carbide whiskers (SiCw) were selected as nonlinear conductive fillers, and composite insulating materials were prepared under five different auxiliary field strengths. On this basis, the orientation degree of the filler in the matrix was quantitatively characterized by X-ray diffraction. Furthermore, the influences of temperature on the dielectric properties of composite materials were studied in three frequency bands: S₁ (100 Hz < f < 5 000 Hz), S₂ (0.01 Hz < f < 100 Hz), and S₃ (0.001 Hz < f < 0.01 Hz). The results show that, as the temperature increases, the dipole polarization loss in the S₁ frequency band continues to increase, the interface polarization loss in the S₂ frequency band gradually decreases, and the conductance loss in the S₃ frequency band shows a trend of first increasing and then decreasing. The above phenomena are consistent with the temperature dependence of the Debye model from a macro perspective, and are related to the charge overcoming probability in the double-potential well relaxation model and the carrier concentration change characteristics in the jump conductance model at the micro level. Finally, the effectiveness of this composite insulating material was verified in suppressing the local field strength distortion of IGBT through finite element simulation. The results show that the transient value and steady-state value of the field strength can be significantly reduced by 38.5% and 90% respectively. The results of this study provide a theoretical basis for the application of composite materials in different operating frequency bands of IGBT.