Abstract: In this paper,the effects of the bound rubber in NR compounds prepared with five different carbon black on stress-strain,rheological properties etc. have been studied.The results showed that the bound rubber contents were increased with increase of structure and surface area of the carbon black filled,which led to the elevation in bulk viscosity,stiffness and green strength, but to the reduction of plasticity and tackyness at low shear rates, and the poorer flow properties and the less shrinkage of extrudates at higher shear rates.In addition,the crosslink density of NR vulcanizates increased with increasing bound rubber content,hence,the modulus,hardness and abrasion resistance of vulcanizates with simultaneous decrease in their tensile strength and elongation.