Abstract: Based on two excavation of Four-season Garden in Zhuhai and the flood channel of Macao University in Hengqin New District the construction sites are both above weak foundation in deep silt with excavation depth of less than 5 meters, which have several accidents during excavation. The analyses of the above two accidents show that they are deep slip failures due to different reasons. Some suitable measures are put forward according to the owers' requirements. The excavation of Four-season Garden is sloped and reinforced, and the excavation for the flood channel of Maco University employs riprapeds and plastic drainage plates and stratification of preloading for the mud after the wall. Hierarchical load in controllable situations of monitoring deformation is adopted, which still needs to be filled to the design elevation of new filling. They result in successful stability of excavation slopes. Several points for accident prevention and measures are summarized so as to provide reference for the design and construction of similar projects.