This study adopts an improved method of the rough set.In view of the typical moraine-dammed lakes in Tibet,China,it is proposed that the moraine lakes prone to outburst often have the five characteristics of steep glacial relief of moraine lake area,frequent glacial activities,large scale of moraine lakes,poor stability of moraine dam,and wet-hot climate condition.Based on the characteristics,evaluation factors are selected in the hazard assessment of moraine-dammed lake outburst.Then,weights are determined for the factors in consideration of practical survey result and verified by fuzzy comprehensive evaluation.By the weights,it can be concluded that the most important factor on outburst is the stability of moraine dam(weight value 0.42),the second is the climate condition(weight value 0.18),and the other three are closely equal(each weight value about 0.13).Width of moraine dam and warm-humid combination are the important influencing factors;lake-glacial distance,lake area,and altitude height are the secondarily important influencing factors;moraine distal flank steepness and average particle size of moraine dam are the ordinary factors.The result of fuzzy comprehensive evaluation is consistent with that of practical survey,so the weights of the high accuracy can be of great reference value to the hazard assessment of moraine-dammed lake outburst in China.