In this paper， taking the rock slope of an open-pit mine in Xizang as an example， based on the site investigation and engineering geological characteristics of mine slope， the engineering geological zoning of mine slope is studied， and the slope stability is qualitatively analyzed and quantitatively calculated by combining the stereographic projection method and Sarma method. The research results show that the slope stability evaluation results were consistent with the current slope status. The slope stability of mining area was not good in general， and the slope in local area has poor stability. Both qualitative and quantitative stability evaluation methods confirm each other， which provides an important basis for slope disaster control design and construction in the next stage， and this has a good reference for similar slope projects.