Considering the piles-raft foundation as a composite system of piles and elastic plate, the interaction between piles-raft foundation and soil is translated into the compatible analysis of force and displacement among piles，elastic plate and ground. Based on different models of foundation subjected to centralized load，the settlement coefficient subjected to uniform load is obtained by means of integral, The flexibility coefficient of piles is calculated by considering the pile as elastic member, and with raft identified as four sides free rectangle plate on the ground, the displacement of raft suffering external loads, counter force of soil and generalized displacement on the boundary could be obtained. A semi-analytical and semi-numerical method， using compatible analysis of force and displacement between piles，elastic plate and ground，is developed to analyze the interaction between piles-raft and subsoil. Numerical analysis prove that the semi-analytical and semi-numerical method is provide an accurate and practical calculation tool to. and meet the needs of practical engineering.