Abstract: Slope failure can be divided into entire slide and local buckling. The collapse risk of slope was judged by investigate safety factor in traditional method, but it was hard to consider the failure risk of slope in different grades. For the complexity of the slope problem, safety factor interval with entire safety factor and local safety factor was applied to research the failure risk of rock slope and heterogeneous slope. The strength reduction method and numerical code were used to compute the maximal and minimum safety factor. The case study indicated that this method could sufficiently reflect the failure possibility of slope, and the obtained safety factor was more credible.