For the design of offshore monopiles to support wind turbines, the monopiles embedded into the ground are replaced with a series of springs, called stiffness matrix. These springs are attached at the surface between the tower and ground to analyze the natural frequency of the overall offshore wind structures, including turbine, tower, and foundations. For these reasons, the p-y curve is an essential parameter for evaluating the monopile''s stiffness matrix and its geotechnical stability. API code adopts on the conventional formula in the past decades, wherein this formula were derived based on field pile load tests with piles with diameter less than 2m. Therefore, many questions have been raised in using the conventional p-y curve from the API code, especially in designing offshore wind turbine monopiles with large diameters. In 2013, the PISA method provided a new strategy in analyzing pile and soil interaction base on the cone penetration tests (CPT). Also, this method were derived from several field test and FEM analysis (using in-situ condition) or combination. As a result an empirical equation (in a form of one dimensional parameters) was produce considering field and lab conditions. However, some issues have been still pointed out when considering shallow depths and multi layered subsurface. Moreover, the availability of physical modelling data on the previous study were not enough in providing more comprehensive analysis relative to the increasing monopile diameter. The aim of this study is to evaluate each formula and provide a comparative analysis for large monopile diameter based on several testing conditions. Thus, the present study performed centrifuge tests to investigate the effect of loading height from the ground surface and end bearing conditions on the p-y curve. In particular, the testing setup was composed of a 7 m-diameter monopile installed in sand and sand-over-rock, with two loading heights of one and five times the monopile diameter from the ground surface. Embedded lengths in the sand were 2.67 (sand-over-rock condition) and 4.67 (uniform sand condition) times monopile diameter. The sand and rock were prepared as "medium sand" and "stiff rock", respectively. The centrifuge model tests were conducted at an acceleration of 68.83g using well-instrumented model monopiles. As a result, the experiment reveals that the p-y curves are not influenced by loading height from the ground surface. It is confirmed that the rock socketed monopile shows a very high initial stiffness of p-y curve. Hence, the findings of the present study confirms the limitations and issues raised by previous research when considering large diameter and shallowly embedded pile foundations for API and CPT based p-y curves, respectively.