Nonlinear electrically conductive composites are widely used for electric field grading in HVDC systems. However, the composites prepared using current methods can rarely simultaneously meet the requirements of a high nonlinear coefficient, low switching field and low filler content, which limits their application scope. In this study, by applying a 10-kHz AC electric field during preparation, the prepared tetra-needle-shaped ZnO whisker/carbon fiber/liquid silicone rubber (T-ZnOw/CF/LSR) composites can be implemented in a manner to meet the above three requirements. The electric field-assisted LSR composites filled with 20 phr T-ZnOw and 5 phr CF can have a switching field as low as 420 V/mm and a nonlinear coefficient up to 11.7. The mechanism for the electric field-assisted enhancement of the nonlinear characteristics of the T-ZnOw/CF/LSR ternary hybrid system is explained based on the electromechanics of the suspended particles. The nonlinear characteristics and the filler content do not present a positive correlation, and a low (< 10 phr) or high (> 30 phr) filler content leads to decreased nonlinear characteristics in the composites. Compared with LSR, the electric field-assisted composites introduce a large number of shallow traps with increased trap density and reduced trap energy levels.