The displacement law of the underground continuous wall and the stress variation of the lateral support in deep foundation pit enclosure structure are the key issues to ensure the safety and stability of the foundation pit during excavation. With the deep foundation pit project of the No. 5 reservoir of Taiyuan Railway Station as the background, fiber-optic light grid sensor is used for long-term monitoring of the ground connection wall and the concrete cross brace, and the influence of temperature on the sensor is taken into account during the monitoring process, on-site monitoring data are modified by temperature compensation measures; Simultaneously, the excavation process of the foundation pit was simulated by using FLAC(3 D). The field monitoring data and numerical simulation results were compared and analyzed, and the trend of ground wall displacement during deep foundation pit excavation was discussed. The research results show that the horizontal displacement of each position of the ground wall at the beginning of earth excavation gradually increases with the increase of the excavation depth of foundation pit. Because the maximum horizontal displacement is located in the middle of the foundation pit when the excavation reaches the base, special attention should be paid to the stress and stability of the lateral support at the middle. The vertical settlement rate of diaphragm wall in the later stage of foundation pit excavation is faster than that in the earlier stage.