Abstract: According to the geological exploration and design materials of Yunnan copper tailings，large dam model are tested on the basis of the proportion of the tailings dam and the on-site damming form.Through analysis on the grain size distribution of samplings from tertiary sub-dam tailings，the regularity of grain size distribution in the tailing dam model are obtained.According to the regularity，two types of tailing sample are classified and tested by the conventional geotechnical tests to achieve the conventional soil mechanics parameters.With the use of the geotechnical numerical simulation software Geo-slope，two kinds of tailings soil physical and mechanical parameters are substituted into the model to calculate the stability under the normal working conditions.The safety coefficient under three damming heights and different damming speed kinds of stacking dam against different speed of dam are calculated out (Among them，the maximum safety factor for the level 4 sub-dam is 2.173 when the damming speed is 5 m/a;the minimum safety factor for level 10 sub-dam is 1.252 when the deposition rate is 15 m/a).The results show that under the same deposition rate，the higher the tailings，the lower the safety factor;As the damming rate increase，the stability of tailing dam with the same height declines.It is necessary to make stability analysis by considering the damming rate of the tailings dam.

Key words: Tailings, Damming rate, Model test, Numerical simulation, Safety factor