An analysis was made on the effects of particle morphology on the mechanical and optical properties of polyvinyl chloride/methyl methacrylate-butadiene-styrene (PVC/MBS) blends. Special care was taken to make comparisons of blends with different structural MBS under same conditions. The blend with a three-layer structure MBS had a lowest brittle-ductile transition (BDT) temperature, while the blend with a two-layer structure MBS had a relatively higher BDT temperature due to its higher Tg of rubber particles enhanced by combination of St. Furthermore, the transparency of blend with two-layer structure MBS was higher than that with three-layer structure MBS. In addition, SEM investigations showed the cavitation of rubber particles took place to remove the plastic constraint and promote a large volume of deformation in the blend with three-layer structure MBS.