Ultra-high-performance-concrete (UHPC) possesses favorable mechanical properties and economy efficiencies and has the potential to be used as the main material to construct tower structures of offshore wind turbines (OWTs). Then the shortages of widely used pure steel OWT towers such as relatively small lateral stiffness, weak fatigue behavior and corrosion resistance can be avoided. In this work, a new type of hybrid tower structure combining a prestressed UHPC tube at the bottom and an upper steel tube is proposed to support a large-size 15 MW OWT. Detailed and carefully refined finite element (FE) analysis by ABAQUS was conducted to explore the dynamic performance of the proposed hybrid tower. The modal properties, dynamic responses, ultimate strength, fatigue strength, and economy performance of the hybrid tower were comprehensively evaluated. It shows that with a similar lateral stiffness but greatly reduced material and maintenance costs compared to a reference steel tower, the hybrid tower has enough ultimate and fatigue strength to resist huge environmental loads caused by extreme winds, waves and earthquakes.