The　monitoring　and　theoretical　studies　for　deep　excavation　are　lack　in　Beijing.　The　monitoring　results　of　deep　excavation　of　China　World　Trade　Center　Tower　phase　3　in　Beijing　during　excavation　process　are　analyzed.　The　study　results　show　that:(1)　Under　normal　circumstances,　the　displacement　of　pile-anchor　bracing　system　is　generally　not　more　than　0.1%H,　where　H　is　the　depth　of　foundation　pit.　(2)　The　stress　of　reinforcement　in　pile　is　usually　only　1/10-1/8　of　design　strength.　(3)　The　actual　tension　of　anchor　is　smaller　than　the　design　value,　which　shows　that　the　adopted　earth　pressure　in　the　design　of　support　system　is　larger　than　the　actual　earth　pressure.　(4)　The　tensions　of　each　row　soil　nailings　are　all　less　than　38　kN,　which　is　far　less　than　the　design　value　calculated　by　current　regulations.　It　is　found　that　the　actual　steel　stress,　anchor　tension　and　soil-nailling　tension　are　all　less　than　the　current　theoretical　values.　The　monitoring　results　can　provide　a　reference　to　the　similar　projects　and　the　basis　for　amendments　to　the　subsequent　procedures.