To evaluate the horizontal bearing capacity of a pile foundation subjected to large lateral load due to earthquake loading, a computation method for the response of laterally loaded reinforced?concrete ( RC) piles was proposed in this study. The computation method was based on the theory of a nonlinear elastic foundation beam, in which the subgrade reaction modulus was calculated by a modified strain wedge model. The material nonlinearity of RC piles was also considered by assigning nonlinear stress?strain relationship to the fibers into which each plane section of RC pile was divided. The results show that:1) the predicted load?deflection curves and deflection pro?files accord well with the measurements;2) the distribution of compressive and tensile stress is symmetrical on the cross?section of the pile until the concrete crack occurs, and after the crack occurs, the neutral axis of the pile cross?section moves forward to the side with compressive stress. It can be concluded that the proposed method can provide an efficient and effective way for laterally loaded reinforced?concrete piles.