This paper presents a support structure for gravity-based horizontal axial tidal current energy conversion system considering factors such as strength, reliability, and costs of transportation and installation, etc. The support structure is an important part which directly affects the operation of tidal energy conversion system. ANSYS Workbench is used to determine stress and deformation of the structure subjected to current loads, wave hydrodynamic loads and inertia loads. Nonlinear contacts effects between framework and base structure are taken into account in our calculation. In order to facilitate offshore installation of framework and base structure, some work is done to explore the effects of contact height between internal and external tube and wall thickness of internal tube to the strength. The results show that the strength and stiffness of support structure comply with the design requirements, and the research work provides a valuable reference for the development of harnessing of tidal energy.