Abstract:Located at the middle and with an embedment up to 700m,the F9 fault is a re?gional trunk fracture. Being extremely complicated, it is the difficult point and the key to build the tunneL Based on the sufficient investigation and research,the paper concludes the tectonic characteristics, the structural characteristics, the behaviour characteristics and the deformation characteristics of the rockmass for F9 fault Therefore, the basis is provided for the tunnel design and construction. In view of different stability conditions of the F9 fault’s surrounding rock, different supporting systems are established and effective construction measures are taken.