Abstract: The occurrence of large deformation in soft rock tunnel with high ground stress is inevitable, which seriously affects the construction safety. Evaluating its stability and judging the deformation trend can provide a certain reference for construction. Taking Songpan tunnel on the Chengdu-Lanzhou railway as an example, the stability and deformation trend judgement model for soft rock tunnel with high ground stress was constructed by using cusp catastrophe theory and Multifractal Detrended Fluctuation Analysis method (MF-DFA) to predict deformation. The results showed that the cusp catastrophe theory can effectively evaluate the stability of large deformation tunnel. Songpan tunnel is in a stable state at present, but the tunnel stability state varies in different stages, and its stability is not only related to the cumulative deformation, but also to the growth process of deformation curve. At the same time, MF-DFA analysis showed that the large deformation of tunnel has multifractal characteristics, and has a small positive growth trend. This method provides a new way for researching the large deformation law of tunnels and can be a reference for engineering design and construction personnel.