Tip leakage flow, which contains multiple spatial and temporal scale flow field structures, is one of the most im-portant sources of aerodynamic losses and unsteady in turbine. In this paper, DDES, Delayed Detached Eddy Sim-ulation, is used to simulate the tip leakage flow in a high-pressure turbine rotor. The structure and unsteady charac-teristics, as well as the unsteady influences between tip leakage flow and wake are analyzed. Based on the un-steady entropy transport equation, the loss mechanism of the leakage flow zone is decomposed and studied. It is found that, the DDES method can finely capture the multiscale flow field structure and mutual interference of the leakage flow and wake; secondly, the result of this paper shows that the interference between the leakage flow and the wake vortex can lead to a significant shift of the wake vortex trajectory, accompanied by the generation of vortex fragmentation phenomenon, which has a strong unsteady effect; based on the unsteady entropy transport equation, the loss caused by vortex fragmentation can account for 23.3% of the pulsation loss, which is a very important source of loss.