Abstract: The carbon nanotubes (CNTs)/styrene-butadiene rubber (SBR) powder composites filled with different contents of CNTs were prepared by the  spray drying method. The dispersion of CNTs in the matrix was investigated. Electrical and dielectric properties of the composites were tested and the corresponding theoretical analysis was discussed. The results show that CNTs are well dispersed in the matrix，which is beneficial for the reinforcement and modification of CNTs on the rubber matrix. Compared with the pure SBR and composites filled with CB，the composites filled with CNTs present a higher dielectric constant and lower dielectric loss under frequencies of 8~18GHz. The electrical conductivity of the composites filled with CNTs is gradually improved with the augment of filled CNTs. Compared with that of pure SBR and composites filled with 60 phr CB，the electrical conductivity of the composites filled with 60 phr CNTs is enhanced by about 10 orders of the magnitudes. There exist contemporary tunnel and percolation conductive mechanism in the CNTs/SBR composites. Powder SBR composites modified with CNTs could be a new type of nanocomposites with excellent comprehensive properties and will be potentially applied in the fields of antistatic rubber，electromagnetic shield, dielectric materials and so on.