Based on the mechanism experiments conducted for the spillway of the Lianghekou hydropower station, this study investigates the variation tendencies of the flow regime, dynamic pressure, air vent cavities, wind speed, and aeration concentration under three types of aeration thresholds. The applicability of formulas for calculating cavity length, gas-water ratio, and water content ratio to the studied project are analyzed, and the derived conclusions could be employed for further investigation on Lianghekou hydropower station and other similar hydraulic projects. Research findings indicate that aeration in the water flow becomes more pronounced with the increasing of spillway discharge, and several hydraulic indicators increase simultaneously, including the root mean square of time-averaged pressure and fluctuating pressure, aeration rate, cavity negative pressure, and cavity length. At a given discharge, the air concentration increases along the spillway, and the vertical distribution of aeration concentration displays successively C-shaped, S-shaped, and I-shaped patterns. According to the research findings, we recommend that Shi Qisui’s formula for cavity length, Chen Zhaohe’s formula for gas-water ratio, and Hall’s formula for water content ratio are most suitable for the estimations of the present study.