Abstract: In the annular cascade test,we aim to observe the fluid field behind the annulus blades,focusing on the velocity field and the vortex shedding frequency in particular,and to investigate the effect of fluid incidence and flux on them.In comparison with the cascade with high positive incidene,the high negative incidence cascade has wider separating section,stronger vortex,and slower wake delay,but weaker vortex intensity.As the incidence approaches the designed value,it can be seen obviously that the separation diminishes and dissipates as the vortices quickly blend with the main flow. Additionally,there is a characteristic frequency valued at 723 Hz in the diverse cases.