Starch/Styrene Butadiene Rubber (SBR) biocomposites were prepared by directly blending of starch and SBR on a two-roll miller. Two types of starch: pure starch and modified starch (M-starch) were used as rubber fillers. M-starch were synthesized by grafting of methyl methacrylate (MMA) monomer onto starch backbone using ceric ammonium nitrate-initiated radical polymerization. Coupling agent styrene-g-(maleic anhydride) (SMA) was used to further improve the interfacial interaction between the filler and rubber matrix. The morphology and mechanical properties of unmodified starch/SBR and M-starch/SBR biocomposites with SMA content of 0, 1, 3, and 5 phr were investigated. SEM observations showed the particle size of M-starch decreased and their dispersion in the SBR matrix significantly improved than unmodified starch. Mechanical properties of M-starch/SBR biocomposites were superior than those of unmodified starch/SBR biocomposites.