With the development of communication technology， increasingly higher communication frequency bands are adopted. However， the electromagnetic wave diffraction capability decreases with increasing frequency. New generation communication systems become more dependent on line-of-sight propagation. Frequent beam switching is required in complex mobile scenarios， which increases excessive system overhead and delay. To address this problem， a position information-assisted grid-based beam switching method is proposed. The feature that the optimal beam pair remains constant in the presence of line of sight（LOS） path is utilized. The grid beam one-to-one correspondence and coverage distribution structure are divided. A position-beam mapping table is establised. All the next switching points and switching information are predicted based on position information and motion speed. The simulation and analysis results show that the proposed method significantly improves the spectral efficiency of the system compared with the non-grid switching method， and the proposed square hexagonal grid switching performance is better than the square grid， and the beam switching probability is reduced by 50%.It guarantees the communication quality and verifies the rationality of the grid-based beam switching method assisted by the position information.