Abstract: At present, the internal force and displacement of anti-slide piles are calculated on the basis of two sections: the loaded segment and the embedded segment (called "Two-section method"). However, this method does not adapt to the situation when the contact surface of the loaded segment and the embedded segment is not a horizontal plane or the bottom of the loaded segment and the top of the embedded segment are not at the same height. The loaded segment is divided into the primary loaded segment and the secondary loaded segment according to the difference of load type and intensity. The cantilevered anti-slide pile is taken as an example, and because the surrounding rock mass of the embedded segment is subjected to the E. Winkler’s assumption, the general formula for calculating the internal force and displacement is derived considering the secondary loaded segment suffering no force or suffering lateral rock-soil pressure (called "Three-section method"). It is demonstrated that the "Two-section method" is just the special case of the "Three-section method". Based on specific engineering examples, the calculated bending moment and shear force on the whole pile by the “T-section method” are mostly smaller than those by the "Three section method" and the deviation is also larger, especially for the embedded segment of anti-slide pile. Therefore, it will bring adverse effect to the engineering safety to design the anti-slide piles according to the "Two-section method".