The separation characteristics of a rotating probability screen having non-blinding and variable sieve openings are theoretically investigated to improve the separation accuracy. The partial separation efficiency of this screen is estimated based on the probability of particle passage through the openings. The separation particle size depends on the rotational velocity of the screen and the included angle of separation rods. As the rotational velocity of the screen increases, the separation accuracy deteriorates. By applying multi-deck screen, the separation accuracy is improved to a sufficient level for practical application.