The vertex reducer located in the compressor disc cavity can reduce the pressure loss of the air system during the process of radial inflow by suppressing the tangential velocity of the air. It plays an important role in improving the efficiency of the engine. At present, the vortex reducers mainly include tube, de-swirling nozzle, fin and baffle. The tubed vortex reducer has the most research and application. But there are some problems, such as large mass and vibration in high-speed rotation. The mass of the de-swirl nozzle is less, but there is also a phenomenon of flow instability. The baffle also has the problems of installation and stability. Some scholars have tried to improve the structure. However, in the current research, there is no theoretical model to describe the total pressure loss. Entropy analysis can be used as a new way to study the mechanism of total pressure loss. Recent studies show that the total pressure loss mainly occurs at the turning point, which is different from the static pressure loss, and also provides ideas for the optimization of the vortex reducer.