The surrounding ground surface settlement laws caused by coupling effect of foundation pit excavation and drainage are summarized based on settlement monitoring data from 4 foundation pits with suspended waterproof curtain in river floodplain by theoretical analysis, empirical formula and finite element numerical simulation method. The results show that: 1) The ground surface settlement can be divided into the main affected area, secondary affected area and weak affected area; the ground surface settlement of main affected area is mainly caused by foundation pit excavation and drainage; and the secondary affected area is mainly caused by drainage. 2) The ground surface settlement curve can be divided into different function expressions according to different affected areas. 3) The distance between the maximum settlement point of the foundation pit and the pit edge xm is 12.0-15.0 m; and the ratio of xm and the excavation depth of foundation pit is about 0.7. 4) The foundation pit excavationinduced ground surface settlement takes 35%; the drainageinduced ground surface settlement takes 65% at the maximum settlement point.