Abstract: The shear strength is an important mechanical index for design of retaining structure for foundation pits, especially in soft soil areas. The index directly determines the success or failure of supporting scheme. Based on an engineering example, by combining field data, five different shear strengths are calculated using Lizheng software for deep excavations. The actual monitoring results are analyzed and verified through finite element analysis. Suitable shear strength indices are proposed for foundation pits in soft soil areas of lacustrine deposits in Kunming.