The double layer subgrade with rigid upper layer and soft lower layer is common in engineering construction. In this paper, the elastic and elasto-plastic analysis on such subgrade by ANSYS was carried out. According to the calculation results of FEM, the plastic zone of subgrade would appear in the upper layer soil of interface, then, it would be expanded up and down with increase of the load. As for the lower layer soil is relatively soft, the plastic zone is expanding rapidly. Finally, as the plastic zone reaches the bottom and the subgrade in the state of ultimate bearing capacity, the calculation starts to be non-convergent. The results can serve as reference to the engineering designers.