Based on theoretical analysis of nonlinear jump of the grain on the existing reciprocating screen, movements of grains on screen working in reciprocal and two new dimensional motion modes were researched respectively by using procedure LS-DYNA, and a dispersion measure was designed to reflect the diversification of grains on the screen, in light of which, the comparative analysis of sifting efficiency of theses three screens was performed. The research established the analytical model according to the real structure and material characteristics of screen and grains. Considering effect of friction and collision of screen to grains and grain to grain, the law of motion of grains was solved out. Results of research showed that the two new dimensional movements of vibration screen make for increase in sifting efficiency. 