Abstract: The deformation and failure law of a high steep slope during transformation from deep open-pit to underground mining using similar material physical models and numerical simulation was researched with Daye Iron Mine as an example. The similar material physical model was monitored with stress sensors, dial-gauge displacement sensors, and close-range photogrammetry methods to obtain the failure and stress-strain characteristics. Systematic analysis was made on displacement and crack failure of surrounding rock to discover the basic deformation and failure law of the high steep slope. The stress distributions, surface subsidence, and plastic zones predicted by a finite-difference numerical model were compared with those measured from the similar material model experiment. The results indicate that the maximum vertical settlement of the high steep slope is 28.2 mm. The extent of damage and the plastic zone in- crease with the mining depth increasing. The shear failure of the rock mass mainly appears at the foot of the two sides slopes. The combination of similar modeling and numerical modeling is a good solution for research on the basic characteristics of rock mass deformation and failure of high-steep slopes during transformation from deep open-pit to underground mining.