Abstract: A numerical simulation was carried out using the finite difference software FLAC3D regarding horizontal deformation of a supporting structure and the resultant surface settlement. A comparison was made using the measured values. The results indicate that: the maximum horizontal displacement of the diaphragm wall occurs at the top of the wall; the horizontal displacement curve presents a “semi-cup” composite form with several inflection points; and the curve of the surface settlement at the rear of the diaphragm wall demonstrates a “concave” form, which complies with the results obtained by monitoring. The Ad/Aq ratio is different because of different construction scenarios and it will decrease with an increasing depth of excavation, which shows that the surface settlement lags. Based on the quantitative analysis of various construction cases, it was determined that the ratio of Ad/Aq is around 0.4 to 0.6. The affected scope of surface settlement induced by pit excavation is mainly distributed at 1.5 times the excavation depth; the d/H value is between 0~1.0 for the main affected zone and 1.0~1.5 for the secondary affected zone. The maximum settlement occurred at the area with a d/H value of 0.5.