Abstract: Based on the idea of optimization design of pile, the composite pile with cast-in-place core is formed with soil-cement pile and cast-in-place pile, which utilizes the virtue of cast-in-place pile and rammed soil-cement pile, and avoids the disadvantage of cast-in-place pile and soil-cement pile. Based on increment theory of elastic-plastic mechanics, a mathematical model for composite foundation with cast-in-place core is established by using Druker-Prager yield criterion for concrete, soil-cement and soil. The finite element program is created by the IFEPG. Through an engineering example, the displacement field，stress field and failure mechanism of composite foundation with cast-in-place core are analyzed.