Based on the monitoring data of a deep foundation pit construction in Tianjin Binhai New Area,this paper analyses the horizontal and vertical displacement of the underground diaphragm wall in the process of super-sized top-down method foundation pit excavation.According the analysis results,the horizontal deformation of the diaphragm wall in top-down method foundation pit,whose distribution is approximately shaped like a bow,changes over the depth of excavation.The maximum horizontal displacement varied significantly between top-down method foundation pit and down-top method foundation pit,occurring at about one-third of the pit depth from the foundation pit excavation surface and in the vicinity of excavation surface,respectively.The wall uplift values,on vertical orientation,increases continuously as the depth of foundation pit becomes increasingly deeper.However,it legs behind each stage of excavation to some extent and tends to be steady after pouring the bottom plate.In addition,the analysis results show that the top-down method has the features of small deformation and strong integrity in contrast with down-top method.