Two carbon nanotubes (CNTs) composites and their electromagnetic interference shielding effectiveness (SE) have been investigated. The CNTs having aspect ratio of 500, 500-1000 and good conductive network are added into composites. The EMI shielding effectiveness (SE) of two composites containing CNTs are achieved up to 20 dB (>;99%). CNTs composites are the promising material as electromagnetic shielding materials for industrial applications. The characterization of morphology of carbon nanotubes and SE measurement results are presented and discussed.