Pneumatic sediment reduction and anti-siltation technology is a new special mechanical sediment reduction technology, which has been applied in areas such as the Xiaolangdi Reservoir, tidal barriers, and high-pile wharfs. However, fundamental research on this technology, including sediment initiation mechanisms, sediment transport efficiency, and key factors for sediment reduction efficiency, remains underdeveloped. This study combined flume experiments with theoretical analysis to address these gaps. Results show that: the bubble motion process in water can be summarized into four stages: formation, development, rising, and diffusion. During the development stage, bubbles extend downward, entraining water and initiating sediment. The downstream surface velocity is approximately inversely proportional to the distance from the measurement point to discharge point. Nozzle aperture, discharge pressure, and discharge duration are the key parameters affecting the performance of sediment flushing. These three parameters generally show a positive correlation with scour volume. These findings contribute to advancing the theoretical foundation of pneumatic sediment reduction.