Electromagnetic shielding composites consisting of hybrid fillers and polyphenylene oxide(PPO)/polyamide 66(PA66) immiscible polymer blends were prepared by melt blending. Carbon black (CB) was used as the foremost conducitve filler and steam exploded sisal fibers (SF) were used as the assistant filler. The cooperation of hybrid fillers and it’s effect on electrical conductivity and electromagnetic interference shielding effectiveness of composites have been investigated. It was observed that SF greatly contributed to effectively decrease the percolation threshold of CB in PPO/PA66 matrix and adsorb carbon particles and PA66 phase of enriched CB particles to form a conductive network. Furthermore, when the mass ratio of CB/SF was 1/1, the electromagnetic shielding effectiveness of PPO/PA66/CB-SF achieved the most excellent performance.