Taking the pile unit and the soil unit for force analysis, the basic differential equations were established.The equivalent stiffness coefficients of the pile and the unit thickness of soil around each pile were developed, taking into account the pile group effect and the interaction between the pile and the soil in the load transfer method.Based on the relation between pile-soil-cushion and boundary conditions, the pile-soil stress ratio and the influence of important parameters were obtained.In the meantime, the pile group effect and the soil lateral pressure were taken into account in the proposed method.The pile-soil stress ratio calculated agrees well with those measured from the model test of pile foundation, showing the rationality of the approach and guiding significance in engineering practice.