To understand the characteristic of deep excavation in soft ground, deep excavation data in ”Tien-Mou” area along MRT Tam-Shui Line were collected. Soil improvement with jet grout is used in all cases. The soil profile, parameters and monitoring data of all cases are carefully evaluated. The relationship between diaphragm wall deflection and jet grout ratio is discussed. The wall deflections after grouting and after excavation are studied, respectively. The axial force of struts are summarized and presented as enveloped earth pressure diagram for design reference. Finally, undrained shear strength and modulus of sub-grade reaction of clay are evaluated by back-analysis.