Calculating the transmitted light intensity of light scattering from random scatters is important for extracting information within the scatterers which is unable to be directly measured or observed. On the basis of analyzing the components of the transmitted light intensity from nano-particle random scatterers, it is pointed out that multiple scattering theory, first-order multiple scattering theory and Lambert-Beer law can be used to calculate the transmitted light intensity in relatively precise degree. The formula of the transmitted light intensity has been deduced too. For a given random system, the said three theories are used to numerically calculate the transmitted intensity and there exist four kinds of typical relationships between the three numerical results. Through analyzing the calculated relationships, the scattering processes within the random scatterers and their contribution to the transmitted light intensity have been analyzed.