The in-situ excavation process of large-section highway tunnels causes significant disturbance to the surrounding rock and poses high construction risks. However, research on the mechanical characteristics of the surrounding rock during in-situ excavation of tunnels is still limited. This paper investigates the mechanical characteristics of surrounding rock under different excavation methods using physical model experiments and a simplified stress model. The results of the tunnel excavation physical model test show that the displacement variation is the largest in the single-sided borehole excavation method, the surrounding rock pressure accumulates at the arch shoulder in the single-sided step excavation method, and the displacement is the smallest with a more uniform surrounding rock pressure distribution in the single-sided CD excavation method. The simplified model analysis of surrounding rock stress indicates that the displacement at the arch foot is larger than at the crown, and the greater the damage degree of the surrounding rock, the larger the displacement. Field measurements confirm that model test values of rock pressure and displacement align closely with measured values, showing similar displacement trends. When the damage coefficient D is 0.2, model values under both methods accurately reflect the measurements. Moreover, the single-sided CD method is more favorable for long-term rock stability. These findings provide theoretical guidance for similar large-section tunnel projects.