Abstract: At present,urban space is becoming increasingly scarce,and the narrow space and complex environment problems faced by excavation of foundation pits in cities have gradually become the key and difficult points in the design of foundation pits.At the same time,most of the foundation pits are excavated in deeper depth under the idea that the whole engineering design is to underground space.Based on the design case of a foundation pit project in Changping District of Beijing,this paper introduces the optimal design of foundation pit in complex environment.The foundation pit is adjacent to the surrounding buildings,and the foundation depth,foundation form,construction age and use function of the surrounding buildings are different.According to the environmental conditions,the pile-anchor supporting system of “multi-elevation+step reduction+different parameters” is designed and adopted,and the dynamic implementation is also carried out in the construction process.Design and management,support structure technology is simple,cost-saving,dynamic and flexible,while ensuring the safety of foundation pit engineering,which can be used for reference for similar projects.