After-harvesting processing of grain is one of the most responsible and energy-intensive opera-tions in its production. Analyzing various designs of separators, it can be concluded that grain cleaning machines with curved working surface on which the centrifugal forces facilitate the passage of the grain mixture through the holes are promising,. The de-sign allows increasing the sift through the sieve by improving the orientation of the grain relative to the holes. The purpose of the study was to find math-ematical dependencies for determining the design parameters of swinging sieves and their drive. The research tasks were to obtain mathematical de-pendences of the rational parameters of the sus-pensions from working condition of the mechanism; to reveal the relationship between the parameters of separator drive. Theoretical studies of the pro-cess of grain separation on sieves with rectangular holes located at the angle to the longitudinal axis of the sieve were carried out with reference to sieve installation. There were obtained the systems of equations of one sieve motion. Based on this mathematical model, a computer simulation model was created. It takes into account the possibility of such design parameters as the sieve parameters, the lengths of the suspensions and the angle of the sieve width to vary. Obtained dependences make it possible to calculate the kinematics of the separa-tor sieves and its design parameters. For the labor-atory sample they were connecting rod length (380 mm), crank (150), as well as the length of sus-pension sieves (350) and bridges (30 mm). In case of a commercial scale separator development these dimensions will be adjusted, but the applied mathe-matical dependencies will remain the same.