Abstract: To study the distribution regularity of nano particles in matrix material theoretically, SiC/PTFE(Poly Tetra Fluoro Ethylene) composites with SiC mass fraction of 3%, 5%, 7% and 9% were used as examples. According to the radius (25 nm), the density (3.2 g/cm³), mass fraction of SiC particles and the density of PTFE matrix material(2.2 g/cm³), 3D simulation models of uniform/deviation distributed nano particles in matrix material were established with 10^-12 g for quality unit and to 25 nm:1 pixel for the scale. Based on box dimensions, dispersions of various cluster/deviation nano particles were characterized quantitatively and verified by mechanical experiment. Experimental results indicate that the box dimension of SiC particles decreases gradually in uniform distribution with the continuous increment of their radius, or the decrement of their volume fractions, and fractal characteristics doesn’t exist in the case of their radius above 100 nm. In another hand, the box dimension of SiC particles (50 nm for radius) decreases gradually in deviation distribution with the continuous increment of their span, or the decrement of their volume fractions, or varying of their distribution from layer and line to reunion, which is less than that in uniform distribution with the same volume fraction, and fractal characteristics doesn’t exist in the case of their span beyond 450 nm. Linear correlations (|R|>0.9) are observed between test results of mechanical properties of SiC/PTFE composites and box dimensions of their 3D simulation models in uniform distribution. Dispersions of nano particles can be characterized quantitatively using box dimension, which can be used to predict macroscopic properties of composites.