Abstract: The windowless spallation target is one of most important components of the accelerator driven sub-critical system. An upward rotation windowless spallation target which chooses water as the working medium was proposed. The target can keep the interface steady and move out the heat in time. The numerical simulation was proceeded by ANSYS Fluent. Through the study it is proved that a steady surface can be kept with this kind of target. There is no whirlpool exists and the velocity below interface as same as the pressure drop under various inlet velocities can be found out.