Abstract: Based on limit equilibrium theory, the effect on pile-soil stress ratio made by cushion thickness on pile and internal friction angle of cushion is analyzed. The calculating formulae of the settlement of pile-soil under foregone pressure is proposed, which account the interaction of pile-soil. Depending on the methods deduced above, the iterative calculating method for pile-soil stress ratio is put forward. A program is written and the samples are calculated. The analyses for results and the comparison with experimental date are presented.