The refined modeling and global reliability design of offshore wind turbine tower system becomes increasing important for ensuring the safety and economy of wind energy harvesting. In this paper, based on the flexible body dynamics and finite element modeling, an integrated model of offshore wind turbine tower system (StoDRAOWT model) is presented, considering the aerodynamic coupling effect, pilesoil interaction, tower fa vibration control and nonlinear torque control. It is then verified against the results obtained from the widely employed software. Moreover, the proposed model is more comprehensive and reasonable, and the computational efficiency is higher. On this basis, the analysis on dynamic response of the whole offshore wind turbine tower system subjected to windwave joint loadings is performed through the refined simulation, which provides the foundation for the stochastic response analysis and reliability design of offshore wind turbine tower systems.