Abstract: Aiming at the problem of calculating the negative friction resistance of pile foundations in large-thickness self-weight collapsible loess sites. First, according to the similarity between the stratified settlement and the vertical displacement solution of Boussinesq. A method is proposed to calculate the soil settlement at any depth around the pile from the total self-weight collapse of the foundation. Secondly, the nonlinearity of the soil and the settlement law of the soil along the radial direction of the pile are considered, and a pile-soil load transfer function that can consider both the nonlinearity and the ultimate shear strength of the soil is proposed, which can calculate the negative skin friction, position of neutral point and settlement of pile top. The calculated results are compared with the measured ones of the field immersion tests on pile foundation, which shows the effectiveness of the proposed method. The research results can provide a new method for the design of pile foundations in collapsible loess sites and also references for the calculation of the bearing capacity of pile foundations in other sites.