Abstract: The calculation in design of mixed support with multi-layer supporting points for deep foundation pit in multi-layer soil affected by the surface loading and ground water is very complex. The authors solved the calculation problem in design of mixed support through finding the commonly used algorithm for the calculation in design of foundation pit, which has arbitrary number of soil layers and arbitrary number of support points, and programmed with a commonly used software. The authors used an object-oriented programming method to design interfaces which is of Windows style, it improved the applicability of software.