This paper analyses the problem of flow aeration for mitigating cavitation on stepped　spillway. The study was conducted on the basis of the data of the spillway model test in a depression tank and the prototype observation for Daochaoshan Hydroelectric Station. The results showed that the large flow aeration to prevent cavitation on the stepped spillway can be solved by the flaring gate pier + stepped spillway. The air entrainment concentration on the bottom of stepped flow is not less than 5%. In the meantime, the results of experiment on higher dam showed that the streamwise air entrainment concentration distribution law does not vary as the dam height is increased by 20 m, so this method of flow aeration can be applied to the stepped spillway of dam height being 131 m.