[Objective] In order to accurately locate the location of the flow energy loss zone and the size of the flow energy loss during the operation of ducted propeller, the flow energy loss characteristics were analyzed from the perspective of energy. [Method] By introducing entropy production theory, the SST k-ω turbulence model and the entropy production equation model was used to carry out ducted propeller steady simulations at different advance coefficients and rotational speeds. [Result] The results show that: the value of viscous dissipation entropy production increases with the increase of advance coefficient, while the value of turbulent dissipation entropy production decreases with the increase of advance coefficient at the same rotational speed. At the same advance coefficient, the two kinds of entropy production value increase significantly with the increase of rotational speed. The proportion of turbulent dissipation entropy production is larger than that of viscous dissipation entropy production at different operating mode, therefore, the main reason for the irreversible flow energy loss of ducted propeller is the turbulent dissipation. The main flow loss zone of ducted propeller is behind the trailing edge of the duct and the hub, in which the hub vortex zone formed behind the hub is exactly the high concentration zone of flow energy loss. In addition, the improved ducted propeller with boss cap fins can significantly improve the vortex distribution at the tail of the propeller and reduce the flow energy loss caused by hub vortex. [Conclusion] The research above reveal the flow loss mechanism of ducted propeller and accurately locate the flow energy loss concentration zone, which can offer new insight for energy-saving optimization design and flow energy loss identification analysis of ducted propeller.