The method for preventing and controlling glacial lake outbreak flood and related debris flows by the present invention is mainly controlling the scale of the floods by separating water and rocks and dispersing its energy step by step. The cascading amplification effects of floods can be reduced by controlling the initiation of source material with energy dissipation by using ground sills, groups of piles, and placed large stones and prefabricated artificial structures. The diversion dam built in the downstream area discharge floods in different layers, which can quickly guide water to the main river. The preconstructed engineering system can be used in a timely manner to prevent and control floods and debris flows induced by a sudden outburst of glacial lakes in areas with important facilities and inhabitants enduring the risk of natural hazards. Prevention and control systems can separate floods and debris flows and dissipate their energy. The groups of ground sills and check dams gradually dissipate the energy of floods, prevent high-energy boulders, and control the initiation of source materials in the channel and bank. Moreover, the systems can also separate the water and rocks in dilute debris flows or debris flows with high bulk densities but low viscosities. The diversion dams also enhance the separation function and keep the flood and debris flow discharge in the lower and upper channel to the main river.