Along with the glacier retreating due to global warming, many cases of glacier lakes outburst and consequent debris flows occurred in alpine areas, which typically resulted in great harms to inhabitant and other downstream infrastructures. Base on flume tests, considering the different combination of unit discharge, reservoir capacity and sediment grain size, the formation of critical conditions and influential factors of debris flow due to glacier lake outburst floods (GLOFs) were studied herein. It is found that whether debris flows be formed or not depend on the capacity of GLOFs and the features of materials in the channel. Analyzing the data obtained from the flume tests reveals that the GLOFs could evolve to debris flow when the parameter K>2.66. The method presented herein could provide theoretical foundation for risk assessment of dangerous glacier lake.