The state of art of tunnel earthquake damages and tunnel earthquake damage mechanism are briefly introduced in this paper. According to tunnel’s traffic function and damage descriptions based on the investigation, tunnel damages are divided into five grades: no damage, minor damage, moderate damage, major damage and collapse, and their corresponding damage index range and characteristic values are defined. The materials of tunnels influenced in Kobe earthquake and Chi-Chi earthquake are collected in this paper, and the damage grades are determined based on the performance in the earthquake. After comparative analysis, the seismic intensity, overburden depth, rock classification, distance from faults and the tunnel length are chosen as the earthquake damage factors. A formula for tunnel seismic damage evaluation
is deducted using these factors and the least square method and with the modification of construction time, seismic fortification intensity and portal stability. The damage of four tunnels is evaluated using the derived formula, and the results are the same with that of static and dynamic methods. It shows that the method provided in this paper is effective, reliable.