Fractal growth in different systems is discussed primarily in this paper. By analyzing the transmission spectra of many kinds of fractal in different systems, we found that the position of the new absorption band in the transmission spectrum was proportional to logarithmic time. Furthermore we found that the whole curve of position of new absorption band as function of logarithmic time could be divided into two straight parts. This shows that while the fractal growth proceeds, there are mainly two different processes according to the fractal speed.