Abstract: Based on the analysis of deformation mechanism of the composite foundation with deep mixing piles,a calculation pattern of the composite foundation was firstly presented according to the unit cell model.Then considering the impact of the distribution behavior of side friction between the pile and the surrounding soil and the effective pile length,the calculation method for the displacement of pile in the treated area was proposed by elastic theory.Thirdly,the settlement calculation method of the underlying stratum was suggested with the solution of Mindlin and Boussinesq.And the settlement calculation of composite foundation with deep mixing piles was presented on the basis of method to determine the distribution of load and the way of determining the depth modulus.The practical engineering calculation indicates that the solution of layer-wise summation method is much bigger.The settlement calculation result of this article is between that of FEM and experimental result,which is lower than that of the existed theoretical methods.The method proposed is simpler than FEM and more rational than the existed theoretical methods.