It is evident that the design of deep foundation pits for underground structure groups in central cities and the safety control of surrounding environments present new development challenges. This study proposes a method for categorizing the critical depth of "deep" and "shallow" foundation pits, clarifies the concept of deep foundation pit engineering systems, emphasizes the scope of environmental safety control, and demonstrates a method for determining the extent of deep foundation pit engineering systems. The overall design approach to deep foundation pits is defined, with constitutive relationships, parameter selection, and scientific verification of soil identified as key technologies for numerical simulation. A comprehensive method and scientific validation approach for parameter selection in numerical models are proposed based on Jinan demonstration city’s parameter system. The integrated design method for deep foundation pits is applied to engineering cases to assess the mechanical properties of existing structures within the (group) system at different excavation stages and actively control their deformation, demonstrating its effectiveness in addressing complex environmental challenges. The overall design approach to deep foundation pits addresses the pressing needs related to “complex environment” and “depth”, utilizing numerical analysis to integrate various media influences such as rock, soil, and underground structures while emphasizing an active principle of “deformation control”, thereby advancing improvements in theory and design methods for deep foundation pits.