Abstract: It is hypothesis that the strength parameters of deep furrow open pit slope varies stably with the time series，and the slope rocks are considered as the continuous，homogeneous and isotropic elastic modulus and jointly bear the gravity stress and horizontal stress at the same time.With the use of the time series modeling，the formula of the forecasting value for the rock mass strength parameters at random time is obtained.Then，taking the oval-shaped rock circle which is on the slope of an oval-shaped furrow pit as the model of the mechanical analysis，and combining with the theory of axial ratio，the Mohr-Coulomb theory and the critical conditions of gliding micro-body in the slope，the oval deep furrow slope' tangential stress expression with the timeliness is deduced，which fits the stable slope shape for the elliptic deep furrow pits.This slope not only can guarantee the slope stability，but also decrease the stripping ratio and improve the economic benefit of the mine.

Key words: Deep furrow open pit, Slope stability, Time series, Axial ratio theory