Abstract: Monopile foundation is the common form in current offshore wind power, and the p-y curve recommended by API is commonly used to obtain the lateral loading of a monopile at present, but it is not applicable to large diameter monopile foundation. The validity of the finite element model of large diameter monopile was verified by an offshore wind power test pile in Fujian, and the damage mode of large diameter monopile and the variation of initial stiffness and ultimate resistance with pile diameter and depth in sand were studied by numerical simulation, and the equations were modified by considering the size effect of pile diameter and burial depth respectively, and finally a modified hyperbolic model was proposed to calculate the p-y curve in sand. The results show that the damage modes of monopiles with different diameters are wedge-shaped damage of shallow soils; the p-y curve calculated by API and hyperbolic model has a large error with the p-y curve obtained by numerical model, while the modified hyperbolic model agrees well with the numerical model results, which can provide reference for the calculation of lateral loading of large-diameter monopiles for offshore wind power in sand.