Abstract: Poly-cis-1, 4-butadiene was dissolved in methyl methacrylate and styrene, the bulk polymerization was carried out at 110℃ An impact transparent MBS resin was obtained. The relationship between the shear rate in bulk polymerization and the morphology of rubber phase, impact strength, gloss, fluidity and transparency of MBS resin had been investigated. The effect of M. W. of matrix on the impact strength was discussed. A new regulator, a-methyl styrene dimer had a similar effect as text-dodeoyl meroaptan in bulk-suspension poly-merization of MBS resin.