Abstract: In order to have a more comprehensive understanding of the influence of foundation settlement on mechanical performance of shear keys of segment joints in immersed tube tunnels, based on the5 immersed tube tunnel project of Hong Kong-Zhuhai-Macao Bridge, large-scare model tests with geometric similarity ratio of 1∶4.69 under two different settlement working conditions are systematically carried out. A finite element numerical simulation on segments of the real immersed tube tunnel is made simultaneously. The mechanical properties of shear key of segment joints and the distribution of shear force are studied. The experimental results show that: (1) The dominant influence on change of stress in the shear keys is induced by the foundation settlement. (2) In the process of foundation settlement, the stress value of the horizontal shear keys is relatively small; (3) The lower end of the angle of shear keys in middle walls is compressed earlier than the same position in side walls, and the former is larger than the latter one in the value of stress, so the shear keys in the middle wall is crushed firstly; (4) The deformation trend of vertical shear keys is that the lower part is being compressed and the upper part is moving apart with shear key trough, the shear force distribution of the roots of shear keys among a joint relates closely with the setting position of shear keys, and in a cross section the foundation subsidence at one side leads to horizontal pull effect on the linings of immersed tube at the other side; (5) The equations for the maximum shear force and foundation settlement in a joint are put forward as well as the vertical shear ratio among the vertical shear force in the joint.