Abstract: The study aims to reveal the variation of material distribution under the sieve with the structural parameters and movement parameters of the cleaning device. The material distribution tests under vibrating screen with different fan speed, fan wind direction angle, crank speed and crank diameter were carried out on QXS-3.0 grain cleaning test bench. By analyzing the content of each material under the sieve and its transverse and longitudinal distribution along the screen surface, the grain weight, impurity weight, total weight of the material and the impurity rate under the screen surface were obtained. The material distribution was very uneven in transverse direction. Buckwheat grains were mainly distributed in the middle position, less on both sides. Due to the influence of fan layout, the impurities were distributed in the shape of Chinese character of “human”. The impurity rate curve of the material under the screen shows a “w” shape distribution and changed obviously with each parameter. In the longitudinal direction, the distribution of materials was not uniform, buckwheat grains were mainly concentrated in the middle of the grain collection box, and the distribution was less in the front and back end. The curves of impurity weight and impurity rate were similar, and they increased slowly in region of 0-1 100 mm, but sharply in 1 100-1 500 mm region. Increasing screen surface and cross flow fan can effectively improve the uniformity of material distribution under the sieve and the cleanliness rate of grain under the sieve. The conclusions can provide theoretical basis for the design of the cleaning device, and also have important significance for guiding production.