The stability of tunnel rock is vital to tunnel construction. By applying the compounding of tectonic systems and tectonic evolution of geomechanics, an analysis has been made on features of single fault crush belts, compound fault crush belts, conjoining fault crush belts, and their influence on stability of tunnel rock, which were confirmed in the field cases of Xiamen sub-sea tunnel. The results show that conjoining fault crush belts and compound fault crush belts can easily lead to unstability of rock, and other factors of faults, such as weathering and the angle between faults strike and tunnel axis strike, also have obvious influence on stability of tunnel rock. The study can offer significant reference for tunnel construction.