Abstract: In the He'ao Tunnel project which is under construction, finite element method (FEM) is utilized to build a 3D refined numerical calculation model for segments and internal structure, and the impact of construction timing of internal structure on the stress performance of segmental lining of the shield tunnel with a super-large cross section is studied through the analysis of the stress and deformation of segments and internal structure at different construction timings of internal structure. The results show that both the transverse stiffness of segment rings and the proportion of segment stress shared by the internal structure would be raised if the internal structure construction started in advance. For example, if the construction timing is advanced from the time when ovality is 5‰ to the time when ovality is 3‰, the extreme values of the deformation of segment and internal structure will be reduced by 28.47% and 32.83% respectively, the extreme values of the stress of segment and its rebars will decrease by 50.0% and 14.4%, and the extreme values of the stress of internal structure and its rebars separately will increase by 70.37% and 19.55%; the construction timing of internal structure has no impact on the deformation and stress distribution law of segment ring and internal structure , but if the internal structure is constructed in advance, the stress of segments and rebars will be distributed more evenly; the internal structure will have a relatively strong ability to suppress the horizontal deformation of segment rings. Taking the case where the construction timing is the time when ovality is 3‰ as an example, the vertical displacement of segments continue to increase by about 19.0% after the construction of internal structure, while the horizontal displacement increases by 0.36% only, and the deformation shape changes from "horizontal duck egg shape" to "butterfly shape" .