The influence of poly(styrene-b-methyl methacrylate) on the interface of PVC/SBSblends is studied by TEM and DMA, When only two pwrcent of PS-b-PMMA is added to PVC/SBS(100/15) blends ,the thickness of the interface get thickened obviously, The molecular weight and the composition of PMMA blocks and PS bolcks have important influence on theinterface of PVC/SBS blends.