Constructing tunnel is a difficult and expensive process which deserves special attention. In this article, cracking behavior in a highway tunnel structure during construction period is researched, including figuring out the causes and evolution of crack. Large deformation of rock mass is the major inducement of the damaging behavior, which is obtained from the field investigation. The layers of the ground were monitored with the displacement of tunnel while the numerical analysis was realized with extended finite element method. The results highlight the regions of cracking on tunnel bottom structure, which emphasizes the accuracy of model and the influence of poor geological condition. This work demonstrates that the carbonaceous slate stratum plays an important role in the stability of tunnel structure, which leads to the phenomenon of stress concentration in tunnel bottom region. Moreover, the implemented numerical model also simulates the process of the damaging behaviors of tunnel structure induced by the poor geological condition, which is similar to the results from field investigation and provides the design basis for maintenance work.