Abstract: Double- arch tunnel is a k ind o f new tunnel form. It has a large span, complica ted structure and cock amam iew orking procedure. Therefore, it is difficult to be constructed under unsymmetrical pressure and comp lex geo log ical cond itions. E specially, a series of eng ineering problems, such as lin ing crack ing and tunne l slope de fo rmation, o ften occur in the entrance po rtal reg ion. Th is paper is based on the pro ject of Fux i tunnel and uses both geo log ical analysis and numerical simulation method. The stress- stra in processes of lining and rock mass are ex am ined systemat ically during the construction of the double- arch tunnel under unsymme trical pressure and com plex geological cond it ions. The comprehensive ana lysis show s that ow ing to the in fluence of theF5 fau l,t fragmenta l structure rockmass w as encountered in the portal reg ion. Due to poor rockmass and unsymmetrical pressure, lining and surrounding rock occurred settlem ent and lateral deform ation after tunne l excavat ion. The slope deformation mode w as creep sliding- fracturing wh ich w as is a result from surround ing rock deformat ion. Based on the above analysis, a conclusion w as drawn that control of the tunnel vau lt deformat ion is a key step to contro l the who le de fo rmation o f the entrance reg ion.