As a typical steep stratified oblique rock slope, Shanyang rockslide in Shaanxi Province is different from buckling failure of inclination-paralleled rockslide, apparent dip slide of inclined bedding rockslide and, what is more, toppling and sliding of steeply inclined rockslide,and belongs to the apparent dip creep-buckling. On the basis of field investigation and analysis of characteristics of structure planes, structure of sliding rockmass and shear outlet, the authors analyzed the failure mode in combination with the buckling mechanism. The authors established and analyzed the buckling mechanical model of steep stratified oblique rock slope under gravity, hydrostatic pressure of groundwater, lateral friction and rockmass depth of the rockslide according to the beam plate theory and mechanical model of bending-buckling failure of slab rent structure rockmass, as well as the condition equation of buckling length. The validity of the condition equation was verified.