To effectively control the safety risks of engineering in crossing underneath operation lines and buildings (structures), the current situation and the challenges of underpass engineering in underground space are analyzed. In addition, the underpass mechanism of underground space is studied based on "dynamic balance," the safety control technology is evaluated, and the direction of future technological developments is suggested. Based on the results, the conclusions are as follows: (1) The undercrossing of underground space is a dynamic process of disturbance and balance among existing buildings (structures), strata, and undercrossing engineering. (2) The analysis of disturbance and control processes is the focus of undercrossing mechanism research. (3) Stability is the target of safe underpasses, and control measures are improved based on existing structures, stratum media, support structures, and dynamic control. (4) Underpass engineering methods can be considered based on factors such as geological conditions, coverage span ratio, surrounding environment, and settlement control requirements. (5) The safety control capacity of existing structures, strata, and supporting structures can be effectively improved via reinforcement and underpinning, stratum improvement and consolidation, isolation, and support.