Abstract：To satisfy the requirement of large engineering problems，evaluation efficiency and accuracy have played important roles in the application of time-domain numerical solution. Based on the damping solvent extraction method(DSEM)，a new sub-regional explicit-implicit recursive method with mixed step-size strategy in time domain is proposed to cope with the numerical analysis of dynamic structure-foundation interaction，which can alternatively apply implicit and explicit integral algorithms with different time steps to the computations of structure region and soil region. This method is convenient to combine the numerical advantages of big calculated time steps in implicit numerical integration and wide applicability for explicit integration. According to the same displacement interpolation relations in single time step for the explicit prediction-correction and implicit Newmark-b integral arithmetic，the deformation compatibility on the interface between structure and soil region can also be naturally guaranteed. Finally，key influential factors for the implementation，such as integral time step and various displacement interpolations on the interface，are also numerically discussed in the detailed practical application，which shows that the new proposed method can efficiently improve the evaluation efficiency under the condition of satisfying engineering accuracy well.
