Abstract: In order to improve the sifting efficiency of plansifter on different materials in the milling system, and improve the quality and efficiency of powder making. The grind of a total of 12 mills, including break system, reduction system, sizing system and tailing roll, obtained from a typical milling production line, was taken as the object of study, to analyze and compare the basic characteristics of each material, and compare the differences in sieving effect under different motion parameters. The results show that the centrifugal acceleration of the flat sieving motion has a significant effect on the sieving effect. When separating the coarse semolina from the material of the front road break system and the sizing system, the best screening effect is achieved when the centrifugal acceleration is ω²r=9.37 m/s², the motion parameters is rotary diameter D=65 mm, and the rotational speed n=162 r/min. The optimum screening effect was achieved at ω²r=10.96 m/s² for the grind of the back-road break system with a motion parameters of D=65 mm; n=188 r/min. For the material of the heart mill system, when using 11XX screen, the material of the front - reduction system has the best screening effect at ω²r=18.51 m/s², motion parameters of D=50 mm; n=260 r/min; the material of the back - reduction system and tail roll system has the best screening effect at 12XX screen when ω²r=20.71 m/s², motion parameters of D=50 mm; n=275 r/min. Therefore, in actual production, the motion parameters of flat screen should be optimally selected according to the system location, particle size characteristics and screening requirements of materials to improve screening efficiency.