Abstract: A 8. 0(m) deep excavation is constructed without any protection immediately adjacent to the building. Because of precipitation the nonuniform settlement for the existing building is brought about when the strength of soil body reduces after the excavation and rain. According to the actual observation, the affected area for ground settlement arisen form precipitation is about 1. 5 times of well depth, the affected area arisen form no-protecting excavation is 3~4 times of pit-depth, and the deformation of soil mass further increases with the reduction of its strength after rain.