Abstract: Tunnel collapsing is a common engineering accident in broken rocky tunnel excavation, which mainly occurred in the working face of tunnel and rock section without supporting. Timely construction method adjustment and advanced collapsing prediction are the effective methods to avoid the accidents. With a collapsing tunnel as the case, the process of collapsing prediction and adjustment of construction method are proposed. Firstly, the collapsing prediction needs to be carried out against rock section without supporting. The upper step height can be assessed by arch rock stability theory and the span limit of tunnel can be determined. The analysis results can be verified by numerical calculation method, and then a reasonable step number can be selected. Secondly, the initial prediction of tunnel working face should be carried out based on geological sketch and numerical calculation are used to carry out secondary assessment. In the light of the important influence of core soil on the stability of tunnel working face, the necessity of method of reserved core soil in step excavation is analyzed. The collapsing prediction and upper step limit vector calculation method based on arch rock stability theory, and the working face stability analysis method based on geological sketch and numerical calculation are proposed.