Abstract: The end-slope is the significant factor of composing the open coal pit，and the reasonable end-slope angle has a great significance on maintaining slope stability and economic benefit.Taking the south end-slope of Haerwusu open coal pit as a case，the numerical finite element method and three ultimate equilibrium methods of Fellenius，Bishop，Janbu were adopted separately to obtain the minimum stability coefficient to be 1.341 on the basis of the slope angle at 37°.There is a potential circular slip surface throughout the entire south end-slope.Its stability is in steady state and has the potential to improve.Based on considering the south end-slope constitutive characteristic and haulage system arrangement，four schemes of improving south end-slope degree were proposed.Numerical finite element method and ultimate equilibrium method of Janbu theory were adopted to analyze slope stability of four feasible programs，the results showed that the slope angle was increased to 40°，and the minimum stability coefficient reached 1.135.By this method，more than 438 thousand ton of coal resources and 181.5 thousand m³ of rock stripping volume were increased，which brings economic benefit of more than 73 820 thousand yuan.

Key words: Surface coal mine, End-slope, Stability analysis, Slope angle optimization