Shield tunneling in soft soil is prone to losing control of posture and seriously deviating from the designed tunnel axis, which can cause significant ground settlement and tunnel misalignment. This paper develops a large-scale indoor shield tunneling model test platform and conducts shield posture adjustment model tests to examine the interaction between the shield and soft soil. Based on these tests, the distribution and evolution of earth pressure and pore water pressure around the shield, as well as the surface displacement under in-situ posture adjustment and tunneling posture adjustment modes are investigated. The results indicate that the earth pressure around the shield and ground displacement are significantly related to the shield tunneling posture mode. When the shield is in the constant posture angle tunneling mode, the sudden changes in earth pressure and ground displacement are mainly due to the in-situ posture adjustment at a large angle before excavation. However, under the subsequent dynamic tunneling effects of the shield shell approaching and leaving the soil in the excavation, the mutation amount gradually dissipates. When the small-range dynamic posture adjustment mode is adopted, the earth pressure around the shield and surface displacement will change synchronously with the shield posture mode and reach their peak value when the posture angle of the shield is maximum. Moreover, there is a plastic limit in the earth pressure around the shield during the posture adjustment, and under the plastic deformation and flow of the soil, the formation will cause soil loss and ground settlement. These findings offer important information on how the shield interacts with the surrounding soil as well as recommendations for constructing shield tunnels in soft soil.