Abstract: The strength composite (SC) pile is a novel type of pile technology which combines high-strength concrete piles and deep cement-mxing (DCM) columns. To attain a theoretical approach for the lateral bearing capacity of SC piles in soft clay, the cement-improved soil is assumed to be the stiff clay. Then, considering the proportion of lateral resistance provided by the cement-improved soil, as well as the soft clay surrounding the pile, the modification factors of p_u and y₅₀ are deduced based on the typical p-y curves for both soft and stiff clays. Subsequently, a modified p-y curve model is initially established to predict the lateral response of SC piles in soft clay. The assessments using the measured response of the SC piles from three field tests are then performed to verify the accuracy and reliability of the proposed p-y curve approach. Furthermore, a parametric study is conducted to clarify the influences of the related parameters on the lateral response of the SC piles. The results illustrate that the proposed analytical approach may effectively predict the lateral response of the SC piles. Evidently, when the lateral deformation of the piles is relatively large, the nonlinear behavior of the concrete-cored piles should be considered. The diameter of the DCM columns (D) has a significant effect on the lateral behavior of the SC piles. Specifically, when the column-pile diameter ratio (D/d) varies from 1.0 to 3.0, the deflections at the pile-head decreases from 25.8 to 5.1 mm at a lateral load level of 120 kN, and the peak bending moment decreases by 51.0%. The lateral performance of the SC piles is greatly affected by the length of the DCM columns (L), however, when the length-diameter ratio (L/d) exceeds 10, the internal force and displacement of the piles stabilize with negligible variation. Additionally, the lateral bearing behavior of the SC piles may also be improved by appropriately increasing the strength of the cement-mixing columns as well as the elastic modulus of the concrete-cored piles.