The reinforcement and nonlinear viscoelastic behavior have been investigated for silica (SiO2) filled solution-polymerized styrene butadiene rubber (SSBR). Experimental results reveal that the nonlinear viscoelastic behavior of the filled rubber is similar to that of unfilled SSBR, which is inconsistent with the general concept that this characteristic comes from the breakdown and reformation of the filler network. It is interesting that the curves of either dynamic storage modulus (G') or loss tangent (tan delta) versus strain amplitude (gamma) for the filled rubber can be superposed, respectively, on those for the unfilled one, suggesting that the primary mechanism for the Payne effect is mainly involved in the nature of the entanglement network in rubbery matrix. It is believed there exists a cooperation between the breakdown and reformation of the filler network and the molecular disentanglement, resulting in enhancing the Payne effect and improving the mechanical hysteresis at high strain amplitudes. Moreover, the vertical and the horizontal shift factors for constructing the master curves could be well understood on the basis of the reinforcement factor f(phi) and the strain amplification factor A(phi), respectively. The surface modification of SiO2 causes a decrease in f(phi), which is ascribed to weakeness of the filler-filler interaction and improvement of the filler dispersion. However, the surface nature Of SiO2 hardly affects A(phi). (c) 2007 Wiley Periodicals, Inc.