Taking rice as the experiment subject, and making scoop offsetting from feed inlet to ensure the quality of cleaning, the influence of the rotation angle and offset distance of the off-centered inlet scoop on the performance of cyclone separating device was studied. Based on the result of this study, the orthogonal test and regression test were also carried out .Through the performance test on cyclone separating device, the following conclusions were obtained. When the diameter of the cyclone separating tube was Φ=350mm, the rotation angle of off-centered inlet scoop was δ=150°, the offset distance of inlet scoop was d=35mm, and the rotation speed of fan was Nf=1200r/min, the cleaning effect was as well favorable, and the cleaning rate was Yq≥99% and the loss rate was Ys≤0.1%. Through the orthogonal test and regression test, the best structural parameters and motion parameters of the cyclone separating device were obtained as following: diameter of the grain export Φ=160mm, rotation speed of the fan Nf=1157r/min, rotation speed of the winnower Ny=1065r/min, cleaning rate Yq=99%, and loss rate Ys=0.06%.