Tensile mechanical properties are important for the characterization of the utilization performances of materials. Inorganic particles are usually used to reinforce and toughen resins and to reduce costs in the polymer industry. It is, therefore, very important to quantitatively appraise the break way and mechanisms and the reinforcing or toughening effect of the fracture surface of tensile specimens. A tensile fracture surface fractal model of particulate-filled polymer composites on the basis of fractal theory is established and a corresponding equation for the tensile fracture surface fractal dimension is proposed in this article. Tensile fracture surface fractal dimensions of particulate-filled polymer composites at filler volume fractions of 2-30% were estimated by means of this equation, and the calculations were compared with the measuring values of calcium carbonate filled acrylonitrile-butadiene-styrene (ABS) resin and titanium dioxide filled ABS resin composites reported in the literature. The results show that the theoretic estimations and the measuring values were roughly close to each other. (c) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 109: 3763-3767, 2008.