Abstract: Spillways are one of the most important structures which are responsible to carry out the high capacity flood discharging into the reservoirs. Due to the combination of high velocity flows and low pressure occurs over these structures and especially close to the rigid boundaries, the potential for cavitation is also raised. Scaled model study of aerators is a common way to investigate the effects of geometries and flow conditions on aeration mechanism. However, these studies are usually concentrated on specific geometry of aerators and flow conditions. In this study, experimental investigation of flow aeration through aerators in chute spillways is investigated. Experiments were performed on different hydraulic models including of Azad, Karkhe, Godar, Shafarood and Nazloochay spillways, in Iran. The study focused on derivation of relationships by using a wide range of geometries and flow conditions to estimate the coefficient of air entrainment. The results show acceptable data, compared with the previous investigation.