Abstract. It was proposed that the gray value distribution contour curve of the fracture surface of material was used to represent the true contour curve of fracture surface, the gray value distribution contour curve was extracted by the image analysis software IPP(Image Pro-Plus), and the fractal dimension of the gray value distribution contour curve of the fracture surface was measured by the structure function method as polypropylene (PP) was the sample, in order to characterize the morphological characteristic of the fracture surface of material. The results indicated that the gray value distribution contour curve could reflect the multilevel of the fracture surface of the material; the fractal dimension of gray value distribution contour curve of PP was 1.6375, the linear degree of fitted by the structure function method was high and the correlation coefficients obtained were more than 0.99. The strong 1inear correlation indicated that impact fracture surface of the PP had significant fractal characteristics. Thus using the fractal dimensions to describe the fracture surface morphology of material may provide a new approach to investigate the morphology of fracture surface of materials.