With a focus on the problems of cavitation damage and the decrease of the energy dissipation rate caused by increasing flow depth and decreasing aeration for traditional stepped spillways under a large discharge rate, a hydraulic jump-aeration stepped spillway was developed, producing aerated flow on the stepped spillways by means of hydraulic jump aeration. Through a physical model test, the air-entrainment characteristics of the hydraulic jump aeration basin were studied, including the effects of the approach flow condition, the length and end sill height of the aeration basin, and hydraulic jump flow regime on air entrainment characteristics. The results demonstrate that the submerged jump shows a better air entrainment effect for the bottom and walls within the aeration basin and the region behind the end sill, and the hydraulic and geometric parameters affect the hydraulic jump flow regime and then affect the air concentration. It is crucial to present a suitable flow regime for air entrainment into the flow on the stepped spillway using the hydraulic jump aeration basin.