Abstract: Aiming at the many uncertain factors in the large deformation risk assessment of deep lying tunnel in complex mountainous area, this study proposes a novel evaluation methodology for squeezing tunnel large deformations based on combined weighting method and unascertained measure theory. Through systematic investigation of large deformation characteristics in high-stress deep-buried tunnels, an evaluation system comprising seven core indicators was established, including the rock compressive strength, elastic modulus, maximum principal stress, surrounding strength-stress ratio, geological structure, surrounding rock grade, and groundwater. By employing a distance function to integrate the Analytic Hierarchy Process (AHP) with entropy weighting method, we developed a combined subjective-objective weighting model that achieves scientifically validated weight allocation for risk assessment indicators of squeezing tunnel large deformations. Based on unascertained measure theory, this study establishes a risk assessment model for large deformations in squeezing tunnels. The model employs linear single-index measure functions to construct a measurement evaluation matrix, and utilizes confidence criterion for determining deformation risk levels. The model was applied to four representative soft-rock tunnels with large deformations: Yangjiaping Tunnel on the Chengdu-Lanzhou Railway, and Lingdana, Langzhen No.2, and Jiangmula Tunnels of a railway in the Yarlung Zangbo River area. Comparative analysis with actual deformation data demonstrated strong agreement between model predictions and field measurements. These results validate the model's effectiveness and accuracy for risk assessment of large deformations in complex mountainous deep-buried tunnels, establishing a novel approach for such geotechnical evaluations.