Abstract: Since both land ends of Xiang’an Tunnel,the first large-scale across-highway subsea tunnel,are situated in water-surrounded highly-weathered rocks,division excavation method is adopted in construction according to the complicated geological situation.Meanwhile,stress monitoring has been conducted on the steel brace which is used as the initial support and the temporary support of the tunnel by vibrating-wire rebar gauges.Based on the monitoring data on the scene,how advanced excavation is conducted in CRD1 & CRD2 and CRD1 & CRD3 separately influences the structural internal force is studied in this paper combined with numerical method.The research shows that the structural internal force is obviously increased when advanced excavation is conducted in CRD1 & CRD2 than in CRD1 & CRD3 and the excavation on CRD3 has a much greater influence on the structural internal force.In a word,the safety factors of both excavation methods can satisfy the needs of the specification,so the structure turns out to be safe.