Principle of light combined with settlement, resulting in a large class of particle size Analyzer, called light sedimentation particle size Analyzer. Water according to the light source, can be subdivided into visible light (white light), laser light and x different types according to different fields are subdivided into two types of gravity and centrifugal force field. When a beam of light passing through a period when there is a suspension of the measuring cell, part of the light is reflected or absorbed, only part of the light reaching the photoelectric sensors, which turn light into electrical signals. Through the light intensity and the suspension of concentrations or particle projection and volume of particle sedimentation in the force field. During the test along with particle classification filter larger particles of light settlement, settlement of small particles, thus, measurements of high resolution, especially when the particle size distribution is irregular, or differential: cloth appeared "multimodal" Qiao situation, the advantages of this approach have become more prominent.