Through the neutralization of magnesium oxide (MgO) and methacrylic acid (MAA), magnesium methacrylate [Mg(MMA)(2)] was in situ prepared in styrene-butadiene rubber (SBR) and used to reinforce the SBR vulcanizates cured by dicumyl peroxide (DCP). The experimental results show that the mechanical properties, dynamic mechanical properties, optical properties, and crosslink structure of the Mg-(MMA)(2)-reinforced SBR vulcanizates depend on the DCP content, Mg(MAA)(2) content, and the mole ratio of MgO/MMA. The formulation containing DCP 0.6-0.9 phr, Mg-MAA(2) 30-40 phr, and MgO/MAA mole ratio 0.50-0.75 is recommended for good mechanical properties of the SBR vulcanizates. The tensile strength of the SBR vulcanizates is up to 31.4 MPa when the DCP content is 0.6 phr and the Mg(MAA)(2) content is 30 phr. The SBR vulcanizates have good aging resistance and limited retention of tensile strength at 100degreesC. The SBR vuleanizates are semitransparent, and have a good combination of high hardness, high tensile strength, and elongation at break. The T-g values of the SBR vulcanizates depend largely on the DCP content, but depend less on the Mg(MAA)(2) content and the MgO/MAA mole ratio. The contents of DCP, Mg(MAA)(2), and the MgO/MAA mole ratio have also great effects on the E' values of the vulcanizates. The salt crosslink density is greatly affected by the Mg(MAA)(2) content and MgO/MAA mole ratio, but less affected by the DCP content.