Based upon the total scattering principle an improvement and development has been made for the measurements of particle sizes and its concentrations. The measurements are carried out with two beams of light with different wavelengths. The accuracy and reliability of measurements can be considerably improved and its measuring range enlarged to a great extent. The principle of this method is dealt with in detail. The experiment arrangement is presented. At the end of this paper the results of measurements obtained by the standard reference materials of polystyrene sphere are also given.