Carbon nanotubes (CNTs) reinforced natural rubber (NR) composite was fabricated in a solvent casting method. The tensile properties and electrical resistivities were investigated. As a comparison, carbon black (CB) reinforced NR was also prepared in the same method. The initial modulus of NR/3 wt% CNT composite was about 1.6 times as large as that of NR/ 3wt% CB composite. NR/CNT composite had a percolation threshold value of about 5 wt% CNTs. The morphology of fillers and composites were observed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The improved properties of NR/CNT composites were attributed to the excellent mechanical and electrical properties of CNTs and its formed network, which must be benefit to electromagnetic interference shielding properties of NR composites.