The fractured surface morphology and the corresponding fractal dimension of poly(vinyl chloride)/methyl methacrylate-butadiene-styrene copolymer (PVC/MBS) blends were investigated by using the secondary electron line method．The results show that the fracture surface or microstructure of nmterlals is not a strict fractal structure

the serf-similarity of the fracture surface only exists in a small range of surveying dimension

and the fractal dimension values for fractured surfaces of different features are difierent from each other The notch impact strength of PVC/MBS blends increased with the increase of the MBS amount and the fractal dimension value dominated by the fractured surface with self-similarity．The relationship be-tween the fracture toughhess of matefials and the fraetal dimension value of fractured surfaces was discussed theoretically．