With the wide use of rigid pile composite foundation, the calculation method for its settlement becomes much and more important. Currently, we mainly take the results of the composite modulus method as a designing reference, but this method is still not accurate yet when we handle soft ground for its exaggeration in pile’s function. From the aspect of settlement generation mechanism, the settlement is caused by two main components: one is the distributed stress on the top surface of the soil determined by soil arching effect; the other is the skin friction distributed along the depth of the pile influenced by pile-soil relative displacement. According to the fundamental principles of soil mechanics, a more accurate calculation method for the settlement in pile’s square layout is proposed based on current research achievements about soil arching effect and pile’s load transfer mechanism; meanwhile, it is programmed with MATLAB-GUI algorithm language for convenience. Through the validation by engineering cases, the calculated results of the program well agree with the observed ones, so the calculation method is feasible in some degree. Furthermore, by comparison with the traditional method, this method has better accuracy. Last but not the least, the program is also easily promoted in practice as it doesnt need to go through the complex process of calculation.