Abstract: In this paper, the fractal dimension were calculated for the tensile fracture surface of PVC / NBR blend thermoplastic elastomer by the island method and the box method, and the differences between the island method and the box method were analysized and compared. According to the calculated results, it indicated that the conclusions were consistent on revealing material microstructure and evaluating the evolution of material fracture,though the calculated results had some differences. In addition, only the proper and appropriate determination method for computing the fractal dimension was chosen, could the fractal characteristics, the material microstructure, the fracture evolution laws ,and the dynamic mechanics of fractal formation be revealed more true and more accurate.