Two dry dock excavation pits in Nansha of Guangzhou are both large in area and quite deep. The soft soil foundation in the pit is already treated by vacuum preloading, and the mud is very thick and its lateral permeability is very poor. Some drainage boards are buried under the soil, and they provide a good channel for the vertical seepageof underground water. Based on the geologic condition, theoretical projections and by launching a study on the deep pilot test area, we select a deep well point precipitation method, which ensures safe and efficient dry construction conditions for the excavation processing, and is proved suitable and rationali for the use of a deep well precipitation. The results of the research may serve as a guide for similar projects, and provide a practical basis for the amendment of Port Engineering Foundation Norms (JTS 147-1—2010).