Time-space dependent effect in process of excavating deep foundation pit is in close relationship with the design of support structure and construction sequence and organization but is mostly dependent on engineering behaviors of soil on site. According to Biot’s consolidation theory and large deformation theory

a coupled model and the method of FEM numerical simulation can be derived with classical variation principle

which is based on Updated Lagrangian formulation of large deformation

As for a real example of engineering

the comparison of the computing results between large deformation and small deformation is shown; and time-space dependent effect of excavating deep foundation pit is analyzed. It is the main conclusion that time-space dependent effect in process of excavation is remarkable and the security of pit using small deformation method is lack.