Electrical conductive polymer composites have significant growth in the manufacture of electrical and electronic components, polymer anodes, various sensors, electromagnetic interference shielding and etc. Compared to metals, conductive polymer composites have some advantages such as low density, ease of shaping, flexibility in design, wide range of electrical conductivity and corrosion resistance. Nowadays, carbon black (CB) particles and carbon fibers are the most commonly used to induce conduction to polymer composites. The aim of this work is to prepare flexible conductive composites for cable anode application. These cables are used for cathodic protection of buried pipes and tanks. In this study, the effect of adding three types of carbon black N550, Ensaco 250 G and Printex XE 2 B, with different structures and specific surface area on EPDM and EPDM/NBR matrix composites were investigated. The electrical resistance of the samples was measured by a four electrode method. Morphology of the samples was studied using scanning electron microscopy. Curing properties of compounds were studied by a rheometer. Mechanical and electrochemical properties of the samples were investigated by tensile test and anodic polarization in Na 2 SO 4 solution. At first, electrical resistivity and percolation threshold of the cured samples with a sulfur system, with different amounts and types of CB in EPDM matrix, were measured. The results showed that by increasing structure and specific surface area, percolation threshold and the electrical resistance of the composites decreased. The percolation threshold for the samples containing Printex, Ensaco and N550, was about 5-10, 20, 30-50 (phr) respectively. The microstructure, distributed particle size and distance between particles, were completely different for the different samples. By increasing structure and surface area, particle size became smaller and the distance between the particles decreased. Also by increasing CB amount in the samples with the same type of CB, the number of CB particles increased and conductive network formed easier. The electrical resistance of EPDM/CB composites containing 30, 70 and 150 (phr) of Printex, Ensaco and N550 was about the same (2.5-3 ohms-cm). This is suitable for use in polymer flexible anodes so they were selected to continue the study. Curing diagrams of these samples showed that the compound containing 150 (phr) of N550 had a very high viscosity that led to the difficult forming process. Tensile test results showed that the sample containing 150 (phr) of N550 had a much higher modulus and lower strength and elongation at break than the other samples. The results of anodic polarization showed that oxidation reaction of water began at higher potentials for the sample containing 30 (phr) of Printex. This led to increase oxidation reaction and less electrochemical environment stability for CB. By comparing mechanical and electrochemical properties and curing diagrams of selected samples, the compound containing 70 (phr) of Ensaco was choose and cured by a peroxide instead of sulfur system. The results showed that electrical resistance of peroxide cured sample was much greater than the sulfur cured sample. This might be due to lower cross-link density in peroxide cured sample. Sulfur and peroxide cured samples had about similar modulus, but strength and elongation at break for peroxide cured sample was greater. Anodic polarization of these samples did not differ. Then, compounds containing 70 (phr) of Ensaco and EPDM were alloyed with different amounts of NBR, and new series of samples were prepared by peroxide curing. The results, showed that by increasing amount of NBR in the composites, electrical resistivity decreased from about 12 ohm-cm for sample without NBR, to about 4 ohm-cm for sample containing 50 (phr) NBR. Also by increasing NBR, modulus increased and strength and elongation at break decreased generally. Anodic polarization of alloyed samples did not show any difference with themselves. Key Words : conductive composite, carbon black, EPDM, polymer anode