Based on dynamic time history analysis, dynamic response behavior of an un supported tunnel through fault zone which was simulated by interface and solid elements was studied under uniform input earthquake wave excitation. The analyses of response behaviors, including displacement difference, acceleration magnification, and plastic zones and so on, were carried out when earthquake wave excitation was input along transverse, longitudinal and vertical of tunnel respectively. The results show that simulation method for fault zone is effective; the earthquake causes obvious displacement difference at fault zone and surrounding rock contacting part. The maximal displacement difference reaches to 51.8mm under transverse uniform input earthquake wave excitation. And the displacement difference under vertical and longitudinal is only 44.3% and 23.1% of the transverse value, respectively; the acceleration magnification in fault zone is significantly greater than that in surrounding rock. Shear failure zone appears at the fault zone and surrounding rock contacting part, and it is especially prominent under input longitudinal earthquake wave excitation. It is proposed that fault zone has significantly influence on the dynamic performance of tunnel. The fault zone and the transitional zones are the control zones of seismic design when tunnel passes through fault zone, thus, the study on the anti seismic measures should be further strengthened.