Abstract: Based on the analysis of floor heave disaster appeared in the Shilin tunnel, and the survey of the field geology of the section, the induction factors of floor heave, such as characteristic of surrounding rock, formation pressure, underground water, supporting conditions and the rheology property are demonstrated. Through analyzing the formation mechanism caused by different induction factors deeply, it is indicated that the disaster appeared in Shilin Tunnel is comprehensive floor heave, which posses the characteristics of water swell, extrusion flow and time effect. Considering the influence of the horizontal fault, the tunnel floor is treated as shell structure, and the estimate formula of the displacement for it is suggested. Moreover, the formula is in the consideration of non-associate inducible factors. The important conclusion is that the bending displacement of the tunnel floor takes up a significant proportion of the total displacement. The above results can further deepen the understanding about the formation mechanism of the floor heave disaster induced by the horizontal fault. And it also provides a reliable reference to the disaster prevention of tunnel floor heave.