Abstract: The Q-scurve of static load tests on single pile is used to calculate the equivalent elastic modulus of the soils under load at all levels. A function relationship between the displacement of pile head and the equivalent elastic modulus is established. The Mindlin solution of displacement is used to calculate the interaction of piles, and an emirical formula is introduced to correct the shortcomings of the elastic solution. The equivalent elastic modulus used to calculate the settlement of pile groups is equal to the elastic modulus calculated from the static load tests on single pile with the same settlement. So the elastic theory can be applied in the plastic stage. Finally, the validity of the proposed method is verified by the field tests.