Abstract: The mucky silty clay of layer ③ and the mucky clay of layer ④ in Shanghai have the characteristics of high water content,fluid plastic state,high compressibility and low strength,classified to the typical soft soil area. Combined with engineering examples,the design points of the deep foundation pit engineering adjacent to the existing building basement in the soft soil area are introduced,and comparative analysis is carried out through theoretical calculation,numerical simulation and monitoring of the implementation process. The results show that for the deep foundation pits in the soft soil area,through the reasonable selection of the type of the retaining structure and the support system,the groundwater treatment and construction conditions are properly formulated,and the process control of foundation pit implementation is strengthened,which could ensure the safety of the foundation pit itself and the surrounding environment.This research can provide reference for the design and construction of similar foundation pit engineering in soft soil area.