A significant sieismic swarm occrrred during July to August of 2020 in Bomi region,eastern part of Tibet,which includes 25 eqrthquakes with M_L≥4.0 and the maximum of M_L4.9 that occurred on July 19. The interval between swarms is of about 24 or 12 hours,which implies that the seismic activity of the Bomi swarm may be triggered by tidal changes with differenct periods. For 20 swarms of M_L≥4.0 earthquakes with focal mechanism solutions,the tidal normal stress,tidal shear stress and tidal Coulomb fracture stress change on two nodels before and after the earthquake have been calculated respectively,and the tidal triggering features of these earthquakes have been discussed. The results illustrate that the tidal strsss has a centain triggering effect on Bomi swarm,and more than 65% cases show an obvious sliding-promoting action on earthquake initiation. The occurring time of these earthquakses are corresponding to the time periods around the maximum tidal normal strsss. This indicates that the enhanced fault tension caused by tidal stress may be one of the major causes for the tidal triggering on Bomi swarm.