Abstract: Calculation analysis has a important weight in engineering investigation and application.Process Oriented Programming(POP)has many disadvantages in readability,code use ratio,exploitation period,maintenance and so on.Therefore combination of the FEM and Object Oriented programming(OOP)method has become a tendency in the filed of geotechnical engineering. The Object Oriented programming of finite element software with language C++ is developed which solves three dimensional interaction problems of raft foundation and soil.It is a useful attempt to study FEM by Object Oriented method.