Abstract: The monopile supporting structure of offshore wind turbine is composed of monopiles, transitions and conical towers. The large variability of Marine Soil and the characteristic of variable cross-section of wind turbine tower greatly increase the number of divided beam elements in finite element calculation of supporting structures using discrete spring method. In order to achieve efficient simulation of monopile supporting structure, an improved Euler-Bernoulli beam element was proposed in this paper. This element realized the built-in relationship between pile and soil, and could consider the variable section effect of tower section. Compared with traditional beam element, the number of divided elements was reduced greatly by using the improved element. The accuracy and efficiency of the improved element was verified in single-layer and multi-layer soil, and the applicability of the element to the calculation of monopile supporting structure was studied. This paper carried out a parameter analysis of monopile lateral bearing capacity, which analyzed the combined influence of pile length and diameter on lateral deformation characteristics and bearing capacity of large diameter piles. And the research suggested a new critical range of relative stiffness eigenvalues between rigid short pile and medium long pile, which is different from that given in existing standard.