Abstract: In order to clarify the failure mechanism and ultimate bearing capacity calculation method of layered sand ground base under strip foundation, the finite element plastic limit analysis method is used to calculate and analyze the layered sand ground base. Through calculation we obtain the upper and lower limit of the ultimate bearing capacity, and analyze varying laws of failure mechanism of ground base with geometric parameters of foundation and mechanical parameters of ground soil. The calculation results are compared with the existing test data and the results of semi empirical formula. On this basis, we divide three failure modes of strip foundation and give corresponding bearing capacity calculation methods. The results show that the failure forms of the foundation can be divided into punching shear failure, transition failure and general shear failure. The simplified calculation method corresponding to the transition failure mode can be used as a reference for practical engineering design.