The dielectric response of charge carriers in disordered materials results from the process of fractal time and the conductance of the fractal structure. The medium metamorphism coal is one kind of structural disordered materials . So, electric polarization feature of coal has been further studied by using fractal geometry theory of time. The result shows that electric polarization property of coal in direct current electric field has fractal characteristic. The relation between b constant of polarization and fractal time dimension is:D t=kb, and the constant k may be relevant to metamorphism degree of coal.