Abstract: A mathematical optimization model which conforming to the p-y curve method is established for laterally loaded pile calculation. The mathematical model solves an unconstrained nonlinear optimization problem and the generalized energy equation is selected as the objective function. According to the p-y curves recommended by China “Code for pile foundation of harbor engineering” and American Petroleum Institute, the work functions of resistance force for soft clay and sand are proposed to conduct the generalized potential energy equation. To uniform the acting range of work function in each element, the soil resistance force is assumed acting on a point where the horizontal displacement equals the average value of upper and lower nodes. With the descent method, the model can be solved directly by general mathematic software packages and have a better adaptability to additional constraints than seeking stationary point by the variational method. Two examples show that the model is effective and practicable.