Research conclusions: ( 1 )The excess deformation of foundation pit can be classified into internal and external factors. The internal factors include the interface of stratum inclining to foundation pit，the weaken of stratum interface because of rainfall，and the weak deformation control of flexible pile - anchor supporting system. The external factors include construction blast and overload due to tower crane on ground. (2) The failure of foundation pit is largely depended on excess deformation，rather than the strength failure of retaining structure. Deformation monitoring and dynamic feedback should be strengthened during construction. ( 3 ) As for the flexible pile - anchor retaining system，limited role for the control of continued deformation is found. The composite retaining system of pile - anchor - support can effectively reduce the tensile stress and deformation of anchor rod， and the stability of foundation pit can be realized. (4) The research conclusions can provide some references for similar project in future.