After mixing different grades of carbon black in NR/BR blends and in NR/SBR blends, we found if the ratio of N2SA to I2NO which indicates the degree of surface active carbon black increased, the amount of bound rubber proportionally increased too. However, the amount of bound rubber per unit specific surface area decreased. Exceptionally NCB-1 black which is the same particle size as the other carbon black increased. This phenomenon can be seen in the NR/BR blends rather than in the NR/SBR blends. In vulcanizing properties, the surface active carbon blacks such as NCB-1, NCB-2 were a short scortch time than ordinary carbon blacks, althogh there were almost no effect to the optimum cure time. Finally, the surface active blacks were superiour to the ordinary blacks in connection with loss of abrasion and loss of cut & chip, especially in the NR/BR blends.