Abstract: Based on a concrete engineering example of oil tanks,a mathematical model for settlement back-analysis is established in this paper by using the traditional layer-wise summation method and the principle of least square method.In the meanwhile,according to the strata subsidence deformation parameters obtained by the water filling test,a settlement back analysis related to the stratum parameters is carried out with the established mathematical model.Thus the equivalent modulus and compression modulus of stratum are calculated;the final subsidence and tilt rate of oil tank foundation are worked out as well.And the results can provide some references for the rectifying plans of oil tank foundation.For the proposed method in this paper,its principle is clear,the model is simple and the calculation is convenient,and it also has reference value and guidance for other similar projects.