Two kinds of scatterings are discussed and the corresponding distribution functions are deduced. The spatial distribution of incoherent backscattering and reflectivity are deduced by simulating the process of stochastic photon movement in random medium using the Monte Carlo method. The results show that different scattering has different reflectivity and spatial distribution of incoherent backscattering. As the angle of incidence increasing, the reflectivity of incoherent backscattering increases. Reflectivity of incoherent backscattering decreases as the absorption coefficient of random medium increasing. By measuring the reflectivity of incoherent backscattering, the absorption coefficient and probability that scattering photon is absorbed by particle each time can be obtained. Reflectivity of incoherent backscattering decreases as the mean free path of photon increases. The mean free path can be gotten by measuring the reflectivity of incoherent backscattering, it is easier than testing coherent backscattering to get the mean free path. Lastly, the effect of backscattering on random laser is discussed.