[Objective] The process and outburst mechanism of moraine dam failure caused by glacier avalanches were studied, in order to provide scientific support for major engineering construction in glacial areas and disaster prevention of glacier lake outburst.[Methods] The model test in flume was carried out with the different volumes of blocks, sliding angle, sliding distance, composition materials and geometric morphology of the dam body. Based on the experimental phenomena, experimental data and theoretical derivation, the process of the surge, the starting mechanism of dam body materials, and the critical condition of outbursts was analyzed.[Results] ① The surge of glacier avalanches decreased with time and distance, and the attenuation was significant with time. ② The outburst process under the surge could be divided into four stages:slope surface erosion, scarp erosion, lateral erosion, and decline. The lateral erosion stage had the largest outburst discharge, the fastest velocity, and the strongest erosion capacity. ③ The starting velocity of particles was given from the perspective of the particle starting mechanism, and the results were in good agreement with that of the Shamov formula. ④ It was verified by the outburst event of Guangxiecuo ice-lake breach in Midui gully, in Bomi County, Linzhi City, Tibet Autonomous Region, and the result is reasonable.[Conclusion] The larger the ice lake storage capacity, the deeper the water depth in front of the dam, the higher the water level rise caused by a glacial landslide, and the more likely the dam body is to outburst. The higher the content of the fine particles in the accumulation of the moraine dam, the stronger the adhesion between the particles, and the more stable the dam body is. The wider the moraine dam and the lower slope foot are, the more stable the dam body is, and the longer the outburst time is.