NanFen open-pit iron mine is one of the largest black metallurgical mines in China with one hundred years of mining history. In recent years, as the mining up of the shallow resources and increasing of mining depth, the local slope reached 552 m (elevation 142-694 m). Because of the "V" shape of main stope section, the space on the bottom of stope became narrow and under the risks of rock rolling, landslides and other disasters. These are serious threats to personnel and mechanical safety. For the problems above, NanFen mine started the new phase of slope expansion and mining. In the last 3 years, landslide disasters have occurred many times during the slope expansion due to the old landslide bodies. In this paper, the characteristics of the whole destruction process of slope rock mass from cracks, expansion, penetration, disintegration and slippage are firstly revealed according to the evolution law of the monitoring and early warning curve of large deformation cable with constant resistance (NPR cable) in “landslide 16-1101”. Then, the mechanical model for large deformation numerical analysis of NPR cable is established using 3DEC, and the whole process that the deposits load of “13-0223 landslide” induced “16-1101 landslide” is numerically simulated. Finally, comparing the measured results and simulated results of destruction characteristics of NPR cable and slope, it is found that there is a significant consistency between them. It is proved that the large deformation numerical analysis model of NPR cable can meet the large deformation of rock mass without being pulled off and broken, thus providing a theoretical basis of large deformation numerical simulation for other similar landslides.