Abstract：Based on the bearing capacity characteristics of vertical pull-out screw pile foundation，the limiting embedded depth of first layer lamina(LED) and the limiting space between of laminas(LSB) are proposed according to Meyerhof bearing capacity theory of deep foundation and limiting equilibrium mechanics. The pull-out failure model of multi-layered screw pile foundation is obtained，and the calculation methods of first LED，the conditional estimation of LSB and the ultimate pull-out bearing capacity of the vertical pull-out screw pile foundation are presented. On the basis of the analysis and the calculated bearing capacity of 14 times vertical pull-out field tests of screw pile foundation，the calculation mistakes of ultimate pull-out bearing capacity of screw pile foundation are less than 10% for the comparing the calculation values to the estimated values of 3 types of screw pile. It shows that the failure model of screw pile foundation is close to the practical situation，and the calculation method can be used to estimate the ultimate bearing capacity of screw pile foundations.
