Some parameters about pore network structure of coal char particle are calculated by nitrogen isotherm adsorption/desorption and SEM measured data. On the basis of the correlation between the fractal dimension and the porosity of a porous solid, fractal models are constructed to represent coal particle and char (39.53% burnoff level) particles, respectively. Using the Monte Carlo method, random numbers with the similar distribution as that of pore radii of coal/char particle are assigned to the lattice sites of fractal models. Transport process on the fractal structure of model is studied with the help of invasion percolation simulation. It is shown that D profiles in case of model (a) has two steps. Percolation threshold of fractal model (a) and (b) are 0.425 and 0.430, respectively. Some critical parameters of coal/char particles are calculated.