Research conclusions: Through the analyses the deformation of strip exterior—protected construction for foundation pit，optimum of measurement spots and analyses of the measured data，the followings are concluded：(1)The horizontal displacement of the exterior—protected construction depends on the excavation depth，width of foundation pit，soil nature，wall rigidity and embedded depth．(2)The measurement spots for the displacement of the wall top should be installed from the span center to both sides evenly，and the measurement spots for the wall should be installed at the supporting place of slightly higher than the deep excavation place with the beginning from the center and from top to bottom．(3)The real—time monitoring should be done in the course of the excavation for predicting the deformation regulation，taking preventive measures in time，lowering the deformation speed and guaranteeing the optimum of measurement spots and the construction safety．