The divertor is one of the core components in the Tokamak magnetic confinement nuclear fusion device, which is responsible for eliminating high-flux energy flow and particle flow. The divertor in China Fusion Engineering Test Reactor (CFETR) is designed to withstand a steady-state thermal load of 10 MW/m² and a transient thermal load up to 20 MW/m². The water-cooled scheme is a promising candidate scheme. The model under high heat flux divertor tube system was established by using RPI wall boiling model and the Eulerian multiphase model. On this basis, the fluid-thermal-structure coupling method is used to simulate the complete structure of divertor blocks. In the steady-state condition, three heat transfer patterns are found and compared in the circumferential and axial directions, and methods to enhance heat transfer (including flow velocity and tube structure) are further evaluated. The results reveal the superiority of the screw tube and the swirl tube in the enhancement of heat transfer with high heat flow. For unsteady conditions, the response of temperature and stress for different components are different. The change of flow boundary quickly affects the whole system, while the thermal shock only poses a great threat to external components, and its influence on internal components is lagging and slight.