Abstract: The protection of groundwater resources has always been a focus in engineering construction. This analysis is based on an underground diaphragm wall water stop project, which is the first construction in the side pilot tunnel of PBA underground excavation station of urban subway in China. MIDAS/GTS NX software is used to simulate the ground settlement changes of the diaphragm wall construction in the pilot tunnel, including before construction, during construction and after construction, and the results are compared with the actual field monitoring data. The results show that: (1) before the construction of the diaphragm wall, the center line of the surface settlement curve is the center line of the station, and the distribution of the curves is obvious symmetrical settlement groove. (2) During the construction of diaphragm wall, when the construction of one-sided diaphragm wall is completed, the settlement near the surface above is the most obvious. The maximum increment account is about 25% of the total settlement. (3) After the construction of diaphragm wall on the left and right sides, the incremental curve of surface settlement amount is similar to W-type. (4) After the construction of 6 diaphragm walls on the left and right sides, the settlement on the surface above tends to be stable, and the settlement rate basically remains unchanged.