The work aims to quantitatively study the effect of different contents of SiC whisker (SiC) on the tensile strength and tensile fracture complexity of polypropylene (PP)/fly ash (FA) composites. Firstly, PP/FA/SiC composites were prepared by melt blending method with PP as the matrix, maleic anhydride graft polypropylene (PP-g-MAH) as the compatibilizer, and FA and SiC as the filler. Secondly, the tensile strength of the composites was tested by the electronic universal tester; meanwhile, the tensile fracture pattern was analyzed by SEM. Then, based on the fractal principle, the fractal dimension of the composite's tensile fracture was calculated by the difference box dimension counting method, and the relationship between the fractal dimension of the tensile fracture and the tensile strength of the composites was analyzed and studied. As a result, the fractal dimension of tensile fracture of the composites was between 1.24 and 1.90, and the correlation coefficient was more than 0.9, which indicated that it had statistically significant self-similarity and strong correlation. In conclusion, the logarithm of the tensile strength of the composites is in a linear functional relationship with the fractal dimension of the fracture.