Abstract: In order to study the effect of rock mass creep on slope stability，as well as to evaluate the safety of open-pit slope during service period，and according to the timeliness slope theory and rock mass creep rule，the expression of long-term strength for mechanics parameters of slope rock mass was analyzed.Also，on the basis of simplified Bishop method in the limit equilibrium method，the calculation formula of circular sliding timeliness stability coefficient was deduced.In addition，the rule was found that the stability coefficient decreased in an exponential fashion with creep time climbing.By studying the timeliness stability of end-slope in the process of steep mining at Haerwusu open-pit mine，results were achieved that with the same lithologic parameters，the integral stability factor of end-slope reduced following a linear fashion with slope angle increasing，the shear strain and shear stress concentrates on the bottom of high and steep steps，and plastic transfixion area shows as circular shape.In addition，as creeping time grows，the timeliness stability factor follows the same rule regardless of different geometric shapes.Rock mass creep property will cause the shear strength and the slope stability factor decreased in an exponential fashion with creep time climbing.Grasp the creep characteristics of rock mass can predict the effective service time of slope，which has very important engineering value.

Key words: Creep, Open-pit mine, Slope stability, Circular sliding, Timeliness slope