Abstract: The Rotational restraint at the top of a pile has an important influence on its behavior under lateral loading. Rotational stiffness, K, and percent fixity, λ, are two parameters commonly used to quantify the pile-head rotational restraint. A p-y method was employed to analyze the responses of a straight flexible pile with partial pile head fixity in sand. It is found that the pile-head displacement and the maximum bending moment below ground approximately linearly vary with λ. Based on the observation, a simple method derived from the CLM method is proposed to calculate the pile-head displacement, the pile-head bending moment, the maximum bending moment underground, and the embedded depth of the maximum bending moment underground of a single pile subjected to lateral loading. The proposed method provides a way to calculate the nonlinear response of laterally loaded single piles with partial pile head fixity by hands. The good accuracy of the proposed method was proved by comparing the results predicted by the method with those by the p-y method.