The failure problem of deep-buried foliated rock tunnel is very prominent, which often presents asymmetry. Moreover, this failure is closely related to foliation occurrence and in-situ stress, and its mechanism is still unclear at present. In this study, a deep buried foliated rock tunnel in a hydropower station was taken as a case, and its failure mechanism was studied by using CASRock software embedded with three-dimensional equivalent continuous mechanical model of foliated rock. On this basis, the relationship and mechanism between the failure of deep-buried foliated rock tunnel and foliation occurrence, in-situ stress and tunnel axis were systematically studied. The results indicate that when the angle between the foliation strike and the tunnel axis (γ) is small, the surrounding rock will experience a larger range of failure. As the γ increases, the depth and degree of failure will significantly decrease. The dip angle of foliation (θ) and the orientation of maximum principal stress determine the failure location of tunnel section. When designing foliated rock tunnels, the angle between the foliation strike and the tunnel axis (γ) should be minimized as much as possible. When the γ is small, more attention should be paid to the orientation of the stress concentration area and its angle with the foliation on the tunnel section after excavation, and support should be strengthened for the small angle parts. This study has important guiding significance for the design, understanding of failure mechanisms, and disaster prevention and control of foliated rock tunnels.