In the study, nylon66/carbon filler composites with different filler types and filler content were fabricated by using a twin-screw extruder at 280 ℃ reference of die temperature. The carbon fillers such as carbon black(CB), multi-walled carbon nanotube(MWCNT), nickel coated carbon fiber(Ni-CF) were used. Double percolation was certified by surface resistivity, rheological properties, and morphological result by SEM when CNT and CB were well dispersed in nylon66 matrix. The surface resistance and the electromagnetic shielding performance of nylon 66/cabin filler composites prepared with various CF contents were examined. Based on surface resistivity and EMI shielding effective, the minimum content of NI-CF was 20 wt% when the EMI shielding effective value has over 40 dB. Compared to hot-press specimen, injection specimen which is advantageous for fiber orientation exhibits a high shielding effect due to Ni-CF orientation toward transverse direction. It is difficult to fabricate the product of the polymer/carbon filler composites with high carbon filler content through the conventional extrusion or injection process due to poor melt flow properties. For this reason, the effect of processing aid and fabricating method on the melt flow and physical properties of the nylon66/carbon filer composites was discussed. As a fabricating method, the master batch for CB and CNT and the change in loading method of Ni-CF were applied respectively. Polyethylene-Wax (L-C102N, L-C121N), 2,2,6,6-Tetramethyl-4-piperidinyl(BIS) were used as the processing aids. In case of nylon66/CB/CNT/CF composites with BIS processing aid, an outstanding improvement of melt flow properties was certified by the complex viscosities and melt flow index and there was little change in electrical properties such as surface resistivity.