Abstract: The influence of refractive index distribution on the frequency property of optical modes in random media is analyzed by using the finite difference time domain method to numerically solve Maxwell equations. The results indicate that the number and the spectral intensity of the modes existed in random media is growing up with the increase of the randomness intensity of the refractive index distribution. The minor variety of the refractive index of scattering granules also can conduce to the increase of the number of the modes in random media. The spectral intensity of these modes is also determined by the excursion, frequency, and velocity of the variety of refractive index of scattering granules. Anisotropic random media can achieve the modulation of the refractive index in terms of time and space. The agreement between experimental observations and simulations is helpful in understanding the physical mechanism in random systems.