Based on Hertz-Mindlin contact model in software EDEM by discrete element method, using linear vibrating screen 360 mm*600 mm, movement characteristics of particle group on sieve plate and law of particles going through sieve plate were studied in screening process of coal in certain conditions, which were as sollows: dip angle was 0°, amplitude was 5 mm, frequency was 11 Hz. The simulation test results show that there are important influences of vibration direction on screening process. And influence law of vibration direction on screening effect was revealed finally. The paper also gained mathematical model between particle group's screening efficiency and vibration direction angle, and mathematical models of particles easy or hard to sieve and material between average movement speeds and vibration direction angle.