The strong fault dislocation caused by earthquake is an important reason for the serious damage on underground structures such as tunnels. Based on the investigation of seismic damage on tunnels caused by the dislocation of left-lateral strike-slip reverse fault during the Menyuan M6.9 earthquake in Qinghai Province, this paper studied the characteristics and causes of the seismic damage, and mainly obtained the following conclusions: (1) The left-lateral strike-slip reverse fault causes serious dislocation of Daliang tunnel, with the maximum horizontal offset of about 1.78 m and the maximum vertical uplift of about 0.68 m. (2) The earthquake damages are mainly concentrated within the influence range of the fault. The severely damaged section of the tunnel is about 350 m, accounting for 5.33% of the total length of tunnel; the less seriously damaged section is located within 402 m at the large mileage side and 646 m at the small mileage side, accounting for 15.96% of the total length of tunnel; the earthquake damage in other sections is generally slight. (3) Construction joints and invert filling layers are more sensitive to strong earthquakes, whose seismic damage is prominent. The beneficial enlightenment obtained from the analysis of seismic damage characteristics in this study can provide reference and guidance for the seismic design of similar projects.