The article reviews different early-warning systems for flash floods and presents China's three-stage prevention system. The first two stages focus on warning methods and achievements, while the third stage proposes a new research idea. Real-time dynamic warning systems can calculate soil moisture, peak flow, and water level to issue flash flood warnings. A compound warning index is used in regions with simple equipment to determine factors like rainfall intensity. The proposed methodology could support flash flood prevention measures in China's development plan. These research findings will guide flash flood monitoring and warning efforts.