Abstract: With the Jianshan Phosphate Mine in Yunnan Phosphate Chemical Group Limited Company engineering background，and in terms of the deformation and instability characteristics of stratified steep dip rock slope，the slope instability process and intrinsic controlling factor have been analyzed by using the cusp catastrophe model.The excavation stability of open-pit slope has been researched with respect to the stress state of the stratified rock slope.The results show as following：（1）With the thickness of strata increasing，lithodeme flexural strength of rock would increase，which could effectively control and prevent from the turn sand twists failure.The rock-soil anchor technology or the step bedding cleaning could reduce risk of this kind of slope instability.（2）With the thickness of bedding slope fixed，the critical slope length would show downward trend with the increase of strata inclination.The thicker the thickness is，the severer the trend becomes.If the inclination is fixed，the critical slope length would show upward trend with the increase of strata thickness.The higher the inclination is，the lower the amplitude becomes.Meanwhile，if the strata inclination is higher than forty degrees，critical slope length increasing amplitude caused by the thicker thickness of strata tends to coincide.The relevant research results provide theoretical and technical guidance and advice for the open pit transportation technology of the mine or mining area with similar conditions.

Key words: Rock bedded slope, Deformation and instability characteristics, Cusp catastrophe model, Stability analysis