Research conclusions:From the research the following settlement characteristics of the underground metro station constructed in soft soil area with top—down method are concluded：(1)The lateral displacement of the concrete diaphragm wall is big in the middle and small on the both ends．The maximum lateral displacement occurs in the area a few meters away from the excavation face．The ratio between the maximum lateral displacement of concrete diaphragm wall and excavation depth is about 0．1 8％．(2)The longitudinal displacement of the wall is mainly of settlement and the most settlements Occur before completion of excavating the second layer．After it the longitudinal displacement of the wall top is in fluctuation state．(3)The soil in the foundation pit and the pile foundation are in swen state during excavation of the foundation pit．，and the swell volume is big in the early—stage excavation．(4)The ground settlement caused by excavation of soil is about 0．13％of the excavation depth．This research achievement can provide the valuable reference to the similar works．